Twilio (TWLO) 10-Q 14 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Entity Registrant Name	TWILIO INC
Entity Central Index Key	1,447,669
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Common Class A
Entity Common Stock, Shares Outstanding		68,822,548
Common Class B
Entity Common Stock, Shares Outstanding		24,207,167

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 91,906	$ 305,665
Short-term marketable securities	192,031	0
Accounts receivable, net	37,258	26,203
Prepaid expenses and other current assets	26,420	21,512
Total current assets	347,615	353,380
Restricted cash	7,450	7,445
Property and equipment, net	47,718	37,552
Intangible assets, net	21,274	10,268
Goodwill	17,407	3,565
Other long-term assets	2,084	484
Total assets	443,548	412,694
Current liabilities:
Accounts payable	7,117	4,174
Accrued expenses and other current liabilities	55,283	59,308
Deferred revenue	13,599	10,222
Total current liabilities	75,999	73,704
Long-term liabilities	12,549	9,543
Total liabilities	88,548	83,247
Commitments and contingencies (Note 10)
Stockholders' equity:
Class A and Class B common stock	93	87
Additional paid-in capital	584,390	516,090
Accumulated deficit	(231,519)	(186,730)
Accumulated other comprehensive income	2,036
Total stockholders' equity	355,000	329,447
Total liabilities and stockholders' equity	$ 443,548	$ 412,694

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Operations
Revenue	$ 100,542	$ 71,533	$ 283,784	$ 195,383
Cost of revenue	48,254	31,285	127,873	86,315
Gross profit	52,288	40,248	155,911	109,068
Operating expenses:
Research and development	31,674	21,106	87,910	53,339
Sales and marketing	25,778	15,873	73,047	47,451
General and administrative	18,867	14,545	40,810	36,773
Total operating expenses	76,319	51,524	201,767	137,563
Loss from operations	(24,031)	(11,276)	(45,856)	(28,495)
Other income, net	1,000	138	1,969	92
Loss before provision for income taxes	(23,031)	(11,138)	(43,887)	(28,403)
Provision for income taxes	(422)	(116)	(902)	(313)
Net loss attributable to common stockholders	$ (23,453)	$ (11,254)	$ (44,789)	$ (28,716)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)	$ (0.13)	$ (0.49)	$ (0.68)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	92,156,768	83,887,901	90,543,087	42,030,989

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (23,453)	$ (11,254)	$ (44,789)	$ (28,716)
Other comprehensive income:
Unrealized loss on marketable securities	(44)		(238)
Foreign currency translation	793		2,274
Total other comprehensive income	749		2,036
Comprehensive loss attributable to common stockholders	$ (22,704)	$ (11,254)	$ (42,753)	$ (28,716)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (44,789)	$ (28,716)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	13,406	5,292
Amortization of bond premium	153
Stock-based compensation	35,973	15,649
Provision for doubtful accounts	407	1,017
Gain on lease termination	(295)
Write-off of internally developed software	96	188
Changes in operating assets and liabilities:
Accounts receivable	(9,173)	(11,275)
Prepaid expenses and other current assets	(4,947)	(11,561)
Other long-term assets	(1,512)	(59)
Accounts payable	1,411	2,317
Accrued expenses and other current liabilities	(1,454)	18,625
Deferred revenue	3,364	3,346
Long-term liabilities	306	9,596
Net cash provided by (used in) operating activities	(7,054)	4,419
CASH FLOWS FROM INVESTING ACTIVITIES:
(Increase) decrease in restricted cash	1,170	(7,439)
Purchases of marketable securities	(280,569)
Maturities of marketable securities	87,325
Capitalized software development costs	(12,281)	(8,447)
Purchases of property and equipment	(8,613)	(5,282)
Purchases of intangible assets	(206)	(646)
Acquisition, net of cash acquired	(22,621)
Net cash used in investing activities	(235,795)	(21,814)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from initial public offering, net of underwriting discounts		160,426
Payments of costs related to public offerings	(430)	(3,936)
Proceeds from exercises of stock options	22,504	4,751
Proceeds from shares issued in ESPP	7,404
Tax benefit related to stock-based compensation		62
Value of equity awards withheld for tax liabilities	(476)	(518)
Net cash provided by financing activities	29,002	160,785
Effect of exchange rate changes on cash and cash equivalents	88
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(213,759)	143,390
CASH AND CASH EQUIVALENTS-Beginning of period	305,665	108,835
CASH AND CASH EQUIVALENTS-End of period	91,906	252,225
Cash paid for income taxes	489	153
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property, equipment and intangible assets, accrued but not paid	124	2,373
Stock-based compensation capitalized in software development costs	2,712	1,068
Vesting of early exercised options	$ 315	512
Costs related to the public offerings, accrued but not paid		$ 368

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2017
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business Twilio Inc. (the “Company”) was incorporated in the state of Delaware on March 13, 2008. The Company is the leader in the Cloud Communications Platform category and enables developers to build, scale and operate real-time communications within their software applications via simple-to-use Application Programming Interfaces, or APIs. The power, flexibility, and reliability offered by the Company’s software building blocks empower entities of virtually every shape and size to build world-class engagement into their customer experience. The Company’s headquarters are located in San Francisco, California and the Company has subsidiaries in the United Kingdom, Estonia, Ireland, Colombia, Germany, Hong Kong, Singapore, Bermuda, Spain, Sweden and Australia.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies (a) Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in our Annual Report on Form 10-K filed with the SEC on February 21, 2017 (“Annual Report”). The condensed consolidated balance sheet as of December 31, 2016, included herein, was derived from the audited financial statements as of that date, but may not include all disclosures including certain notes required by U.S. GAAP on an annual reporting basis. In the fourth quarter of 2016, the Company adopted the guidance of Accounting Standard Update (“ASU”) No. 2016-09, “Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” , which simplified several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures, statutory tax withholding requirements and classification in the statement of cash flows. The Company adopted all provisions on either prospective or modified retrospective basis. The impact from any of the adopted provisions was immaterial to the Company’s financial position, results of operations and cash flows. Hence, prior periods were not adjusted. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive loss and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2017 or any future period. (b) Principles of Consolidation The condensed consolidated financial statements include the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated. (c) Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates are used for, but not limited to, revenue allowances and returns; valuation of the Company’s stock and stock-based awards; recoverability of long-lived and intangible assets; capitalization and useful life of the Company’s capitalized internal-use software; fair value of acquired intangible assets and goodwill; accruals and contingencies. Estimates are based on historical experience and on various assumptions that the Company believes are reasonable under current circumstances. However, future events are subject to change and best estimates and judgments may require further adjustments; therefore, actual results could differ materially from those estimates. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation. (d) Concentration of Credit Risk Financial instruments that potentially expose the Company to a concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, restricted cash and accounts receivable. The Company maintains cash, cash equivalents, restricted cash and marketable securities with financial institutions that management believes are financially sound and have minimal credit risk exposure. The Company sells its services to a wide variety of customers. If the financial condition or results of operations of any one of the large customers deteriorate substantially, operating results could be adversely affected. To reduce credit risk, management performs ongoing credit evaluations of the financial condition of significant customers. The Company does not require collateral from its credit customers and maintains reserves for estimated credit losses on customer accounts when considered necessary. Actual credit losses may differ from the Company’s estimates. As of September 30, 2017, one customer organization represented approximately 11% of the Company’s gross accounts receivable. As of December 31, 2016, one customer organization represented approximately 16% of the Company’s gross accounts receivable. In the three and nine months ended September 30, 2017, no customers represented more than 10% of the Company’s total revenue. In the three months ended September 30, 2016, one customer organization represented 15% of the Company’s total revenue, and in the nine months ended September 30, 2016, two customer organizations represented 10% and 13% of the Company’s total revenue. (e) Significant Accounting Policies There have been no changes to our significant accounting policies described in our Annual Report. (f) Recently Issued Accounting Guidance, Not yet Adopted In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Updates (“ASU”) 2017-09, “ Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting” , which clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. The guidance is effective prospectively for interim and annual periods beginning after December 15, 2017 and early adoption is permitted. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Test for Goodwill Impairment ”, which removes the second step of the goodwill impairment test that requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. This guidance is effective prospectively for interim and annual reporting periods beginning after December 15, 2019. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In January 2017, the FASB issued ASU 2017-01, “ Business Combinations (Topic 805) Clarifying the Definition of a Business”, which amends the guidance of FASB Accounting Standards Codification Topic 805, “ Business Combinations ”, adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted under certain circumstances. The Company will evaluate the impact of this guidance on its financial statements and related disclosures next time there is a potential business combination. In November 2016, the FASB issued ASU 2016-18, “Restricted Cash” , which requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash and restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted. The Company will adopt this guidance upon its effective date. The restricted cash balances as of September 30, 2017 and December 31, 2016 were $7.4 million and $8.6 million, respectively. In October 2016, the FASB issued ASU 2016-16, “Intra-Entity Transfers Other Than Inventory” , which requires entities to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments” , which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses. ASU 2016-13 is effective for annual and interim periods beginning after December 15, 2019 and early adoption is permitted for annual and interim periods beginning after December 15, 2018. The Company is evaluating the impact of this guidance on its condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, “ Leases” . The standard will affect all entities that lease assets and will require lessees to recognize a lease liability and a right-of-use asset for all leases (except for short-term leases that have a duration of less than one year) as of the date on which the lessor makes the underlying asset available to the lessee. For lessors, accounting for leases is substantially the same as in prior periods. For public companies, the new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. For leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, lessees and lessors must apply a modified retrospective transition approach. While the Company expects the adoption of this standard to result in an increase to the reported assets and liabilities, the Company has not yet determined the full impact that the adoption of this standard will have on its condensed consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, “ Revenue from Contracts with Customers ”. This new guidance will replace most existing U.S. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU 2015-14 which deferred, by one year, the effective date for the new revenue reporting standard for entities reporting under U.S. GAAP. In accordance with the deferral, this guidance will be effective for the Company beginning January 1, 2018 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. In March 2016, the FASB issued ASU 2016-08, “ Revenue from Contracts with Customers, Principal versus Agent Considerations (Reporting Revenue Gross versus Net)” clarifying the implementation guidance on principal versus agent considerations. Specifically, an entity is required to determine whether the nature of a promise is to provide the specified good or service itself (that is, the entity is a principal) or to arrange for the good or service to be provided to the customer by the other party (that is, the entity is an agent). The determination influences the timing and amount of revenue recognition. In April 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing,” clarifying the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments also provide implementation guidance on determining whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time). In May 2016, the FASB issued ASU 2016-12 “Revenue from Contracts with Customers (Topic 606), Narrow-Scope Improvements and Practical Expedients,” which amends the guidance on transition, collectability, noncash consideration and the presentation of sales and other similar taxes. ASU 2016-12 clarifies that, for a contract to be considered completed at transition, all (or substantially all) of the revenue must have been recognized under legacy GAAP. In addition, ASU 2016-12 clarifies how an entity should evaluate the collectability threshold and when an entity can recognize nonrefundable consideration received as revenue if an arrangement does not meet the standard’s contract criteria. In September 2017, the FASB issued ASU 2017-13, “ Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842)” . These amendments provide additional clarification and implementation guidance on the previously issued ASUs. These amendments do not change the core principles of the guidance stated in ASU 2014-09, instead they are intended to clarify and improve operability of certain topics included within the revenue standard. The effective date and transition requirements for ASU 2016-08, ASU 2016-10 and ASU 2016-12 are the same as the effective date and transition requirements for ASU 2014-09. The Company performed its preliminary evaluation and selected a modified retrospective transition method with cumulative effect adjustment as of the standard’s effective date. While the Company has not yet completed the full analysis, based on the evaluation to date, the Company does not expect the adoption of this guidance to have a material impact on its financial position, results of operations or cash flows.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements The Company records certain of its financial assets at fair value on a recurring basis. The Company’s financial instruments, which include cash, cash equivalents, accounts receivable and accounts payable, are recorded at their carrying amounts, which approximate their fair values due to their short-term nature. Restricted cash is short-term and long-term in nature and consists of cash in a savings account, hence its carrying amount approximates its fair value. Marketable securities consist of U.S. treasury securities and high credit quality corporate debt securities. All marketable securities are considered to be available-for-sale and are recorded at their estimated fair values. Unrealized gains and losses for available-for-sale securities are recorded in other comprehensive income (loss). Impairments are considered to be other than temporary if they are related to deterioration in credit risk or if it is likely that the security will be sold before the recovery of its cost basis. Realized gains and losses and declines in value deemed to be other than temporary are determined based on the specific identification method and are reported in other income (expense), net. The following tables summarize the Company’s financial assets as of September 30, 2017 and December 31, 2016 by type (in thousands): Amortized Cost Net Fair Value Hierarchy as of September 30, 2017 Aggregate Fair Value Losses Level 1 Level 2 Level 3 Value Financial Assets: Cash and cash equivalents: Money market funds $ $ — $ $ — $ — $ Total included in cash and cash equivalents — — — Marketable securities: U.S. Treasury securities ) — — Corporate debt securities ) — — Total marketable securities ) — Total financial assets $ $ ) $ $ $ — $ There were no marketable securities as of December 31, 2016. Carrying Fair Value Hierarchy as of December 31, 2016 Aggregate Fair Value Level 1 Level 2 Level 3 Value Total Financial Assets: Money market funds (included in cash and cash equivalents) $ $ $ — $ — $ Total financial assets $ $ $ — $ — $ The Company classifies its marketable securities as current assets as they are available for current operating needs. The following table summarizes the contractual maturities of marketable securities as of September 30, 2017 (in thousands): Amortized Aggregate Fair Cost Value Financial Assets: Less than one year $ $ One to two years Total $ $ For fixed income securities that had unrealized losses as of September 30, 2017, the Company has determined that no other-than-temporary impairment existed. As of September 30, 2017, all securities in an unrealized loss position have been in an unrealized loss position for less than one year. Interest earned on marketable securities in the three and nine months ended September 30, 2017 was $0.7 million and $1.8 million, respectively, and is recorded as other income (expense), net, in the accompanying condensed consolidated statements of operations.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2017
Property and Equipment
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): As of As of Capitalized software development costs $ $ Leasehold improvements Office equipment Furniture and fixtures Software Total property and equipment Less: accumulated depreciation and amortization ) ) Total property and equipment, net $ $ Depreciation and amortization expense was $3.4 million and $9.3 million for the three and nine months ended September 30, 2017, respectively, and $1.9 million and $4.9 million for the three and nine months ended September 30, 2016, respectively. The Company capitalized $5.5 million and $15.0 million of software development costs in the three and nine months ended September 30, 2017, respectively, and $3.4 million and $9.5 million in the three and nine months ended September 30, 2016, respectively. Of this amount, the stock-based compensation expense was $1.2 million and $2.8 million in the three and nine months ended September 30, 2017, respectively, and $0.4 million and $1.1 million in the three and nine months ended September 30, 2016, respectively. Amortization of capitalized software development costs was $2.2 million and $5.9 million in the three and nine months ended September 30, 2017, respectively, and $1.4 million and $3.7 million in the three and nine months ended September 30, 2016, respectively.

Recent Acquisition

Recent Acquisition	9 Months Ended
	Sep. 30, 2017
Recent Acquisition
Recent Acquisition	5. Recent Acquisition On February 6, 2017, the Company completed its acquisition of a messaging provider based in Sweden specializing in messaging and SMS solutions, for a total purchase price of $23.0 million, paid in cash, of which $5.0 million was held in escrow. The escrow will continue for 18 months after the transaction closing date and may be extended under certain circumstances. Additionally, the Company deposited $2.0 million into a separate escrow account that will be released to certain employees on the first and second anniversaries of the closing date, provided the underlying service conditions are met. This amount is recorded as prepaid compensation in the accompanying condensed consolidated balance sheet and is amortized into expense as the services are rendered. The acquisition was accounted for as a business combination and, accordingly, the total purchase price was allocated to the preliminary net tangible and intangible assets and liabilities based on their preliminary fair values on the acquisition date. The prepaid compensation subject to service conditions is accounted for as a post-acquisition compensation expense and recorded as research and development expense in the accompanying condensed consolidated statement of operations. We expect to continue to obtain information to assist us in determining the fair values of the net assets acquired on the acquisition date during the measurement period. The acquired entity’s results of operations have been included in the condensed consolidated financial statements of the Company from the date of acquisition. The following table presents the preliminary purchase price allocation recorded in the Company’s condensed consolidated balance sheet on the acquisition date, and as subsequently adjusted during the three months ended June 30, 2017 (in thousands): Total Net tangible liabilities $ ) Goodwill (1) Intangible assets (2) Total purchase price $ The Company acquired a net deferred tax liability of $2.6 million in this business combination. (1) Goodwill represents the excess of purchase price over the fair value of identifiable tangible and intangible assets acquired and liabilities assumed. The goodwill in this transaction is primarily attributable to the future cash flows to be realized from the acquired technology platform, existing customer and supplier relationships as well as operational synergies. (2) Identifiable finite-lived intangible assets were comprised of the following: Total Estimated Developed technology $ 4 Customer relationships 7-8 Supplier relationships 5 Total intangible assets acquired $ The estimated fair value of the intangible assets acquired was determined by the Company, and the Company considered or relied in part upon a valuation report of a third-party expert. The Company used income approaches to estimate the fair values of the identifiable intangible assets. Specifically, the developed technology asset class was valued using the-relief-from royalty method, while the customer relationships asset class was valued using a multi-period excess earnings method and the supplier relationships asset class was valued using an incremental cash flow method. The Company incurred costs related to this acquisition of $0.7 million, of which $0.3 million and $0.4 million were incurred during the fiscal years 2017 and 2016, respectively. All acquisition related costs were expensed as incurred and have been recorded in general and administrative expenses in the accompanying condensed consolidated statements of operations. Pro forma results of operations for this acquisition have not been presented as the financial impact to the Company’s condensed consolidated financial statements is immaterial.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2017
Intangible Assets
Intangible Assets	6. I ntangible Assets Goodwill Goodwill balance as of September 30, 2017 and December 31, 2016 was as follows: Total Balance as of December 31, 2016 $ Goodwill recorded in connection with the recent acquisition Measurement period adjustment ) Effect of exchange rate Balance as of September 30, 2017 $ Intangible assets Intangible assets consisted of the following (in thousands): As of September 30, 2017 Gross Accumulated Net Amortizable intangible assets: Developed technology $ $ ) $ Customer relationships ) Supplier relationships ) Trade name ) — Patent ) Total amortizable intangible assets ) Non-amortizable intangible assets: Domain names — Trademarks — Total $ $ ) $ As of December 31, 2016 Gross Accumulated Net Amortizable intangible assets: Developed technology $ $ ) $ Customer relationships ) Trade name ) Patent ) Total amortizable intangible assets ) Non-amortizable intangible assets: Domain names — Trademarks — Total $ $ ) $ Amortization expense was $1.5 million and $4.2 million for the three and nine months ended September 30, 2017, respectively, and $0.1 million and $0.4 million for the three and nine months ended September 30, 2016, respectively. Total estimated future amortization expense was as follows (in thousands): As of 2017 (remaining 3 months) $ 2018 2019 2020 2021 Thereafter Total $

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	9 Months Ended
	Sep. 30, 2017
Accrued Expenses and Other Liabilities
Accrued Expenses and Other Liabilities	7. Accrued Expenses and Other Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): As of As of 2017 2016 Accrued payroll and related $ $ Accrued bonus and commission Accrued cost of revenue Sales and other taxes payable ESPP contributions Deferred rent Accrued other expense Total accrued expenses and other current liabilities $ $ Long-term liabilities consisted of the following (in thousands): As of As of 2017 2016 Deferred rent $ $ Deferred tax liability — Accrued other expense Total other long-term liabilities $ $

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	9 Months Ended
	Sep. 30, 2017
Supplemental Balance Sheet Information
Supplemental Balance Sheet Information	8. Supplemental Balance Sheet Information A roll-forward of the Company’s reserves is as follows (in thousands): (a) Allowance for doubtful accounts (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Balance, beginning of period $ $ $ $ Additions Write-offs — ) ) ) Balance, end of period $ $ $ $ (b) Sales credit reserve (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Balance, beginning of period $ $ $ $ Additions Deductions against reserve ) ) ) ) Balance, end of period $ $ $ $

Revenue by Geographic Area

Revenue by Geographic Area	9 Months Ended
	Sep. 30, 2017
Revenue by Geographic Area
Revenue by Geographic Area	9. Revenue by Geographic Area Revenue by geographic area is based on the IP address at the time of registration. The following table sets forth revenue by geographic area (dollars in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Revenue by geographic area: United States $ $ $ $ International Total $ $ $ $ Percentage of revenue by geographic area: United States % % % % International % % % %

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies
Commitments and Contingencies	10. Commitments and Contingencies (a) Lease Commitments The Company entered into various non-cancelable operating lease agreements for its facilities over the next seven years. Certain operating leases contain provisions under which monthly rent escalates over time. When lease agreements contain escalating rent clauses or free rent periods, the Company recognizes rent expense on a straight-line basis over the term of the lease. Rent expense was $2.1 million and $6.1 million for the three and nine months ended September 30, 2017, respectively, and $2.1 million and $5.1 million for the three and nine months ended September 30, 2016, respectively. Future minimum lease payments under non-cancelable operating leases were as follows (in thousands): Year Ending December 31: As of September 30, 2017 (remaining three months) $ 2018 2019 2020 2021 Thereafter Total minimum lease payments $ (b) Legal Matters On April 30, 2015, Telesign Corporation, or Telesign, filed a lawsuit against the Company in the United States District Court, Central District of California (“Telesign I”). Telesign alleges that the Company is infringing three U.S. patents that it holds: U.S. Patent No. 8,462,920 (“‘920”), U.S. Patent No. 8,687,038 (“‘038”) and U.S. Patent No. 7,945,034 (“‘034”). The patent infringement allegations in the lawsuit relate to the Company’s Programmable Authentication products, its two-factor authentication use case and an API tool to find information about a phone number. The Company has petitioned the U.S. Patent and Trademark Office (“U.S. PTO”) for inter partes review of the patents at issue. On July 8, 2016, the U.S. PTO denied the Company’s petition for inter partes review of the ‘920 and ‘038 patents. After the U.S. PTO held its hearing on the ‘034 patent inter partes review, on June 26, 2017, it upheld the patentability of the ‘034 patent, adopting Telesign’s narrow construction of its patent. On March 28, 2016, Telesign filed a second lawsuit against the Company in the United States District Court, Central District of California (“Telesign II”), alleging infringement of U.S. Patent No. 9,300,792 (“‘792”) held by Telesign. The ‘792 patent is in the same patent family as the ‘920 and ‘038 patents asserted in Telesign I. On March 8, 2017, in response to a petition by the Company, the U.S. PTO issued an order instituting the inter partes review for the ‘792 patent. A final written decision is expected by March 2018. On March 15, 2017, Twilio filed a motion to consolidate and stay related cases pending the conclusion of the now instituted ‘792 patent inter partes review. On May 16, 2017, the court issued an order to consolidate the Telesign I and Telesign II matters and stay the consolidated case until the completion of the inter partes review of the ‘792 patent. With respect to each of the patents asserted in Telesign I and Telesign II, the complaints seek, among other things, to enjoin the Company from allegedly infringing the patents, along with damages for lost profits. On December 1, 2016, the Company filed a patent infringement lawsuit against Telesign in the United States District Court, Northern District of California, alleging indirect infringement of United States Patent No. 8,306,021, United States Patent No. 8,837,465, United States Patent No. 8,755,376, United States Patent No. 8,736,051, United States Patent No. 8,737,962, United States Patent No. 9,270,833, and United States Patent No. 9,226,217. Telesign filed a motion to dismiss the complaint on January 25, 2017. In two orders, issued on March 31, 2017 and April 17, 2017, the Court granted Telesign’s motion to dismiss with respect to the ‘962, ‘833, ‘051 and ‘217 patents, but denied Telesign’s motion to dismiss as to the ‘021, ‘465 and ‘376 patents. This litigation is currently ongoing. On February 18, 2016, a putative class action complaint was filed in the Alameda County Superior Court in California, entitled Angela Flowers v. Twilio Inc. The complaint alleges that the Company’s products permit the interception, recording and disclosure of communications at a customer’s request and are in violation of the California Invasion of Privacy Act. The complaint seeks injunctive relief as well as monetary damages. On May 27, 2016, the Company filed a demurrer to the complaint. On August 2, 2016, the court issued an order denying the demurrer in part and granted it in part, with leave to amend by August 18, 2016 to address any claims under California’s Unfair Competition Law. The plaintiff opted not to amend the complaint. Discovery has already begun, and a hearing on the class certification motion is set for December 2017. The Company intends to vigorously defend these lawsuits and believes it has meritorious defenses to each matter in which it is a defendant. It is too early in these matters to reasonably predict the probability of the outcomes or to estimate ranges of possible losses. In addition to the litigation matters discussed above, from time to time, the Company is a party to legal action and subject to claims that arise in the ordinary course of business. The claims are investigated as they arise and loss estimates are accrued, when probable and reasonably estimable. While it is not feasible to predict or determine the ultimate outcome of these matters, the Company believes that these legal proceedings will not have a material adverse effect on its financial position or results of operations. (c) Indemnification Agreements The Company has signed indemnification agreements with all of its board members and executive officers. The agreements indemnify the board members and executive officers from claims and expenses on actions brought against the individuals separately or jointly with the Company for certain indemnifiable events. Indemnifiable Events generally mean any event or occurrence related to the fact that the board member or the executive officer was or is acting in his or her capacity as a board member or an executive officer for the Company or was or is acting or representing the interests of the Company. In the ordinary course of business, the Company enters into contractual arrangements under which it agrees to provide indemnification of varying scope and terms to business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of the breach of such agreements, intellectual property infringement claims made by third parties and other liabilities relating to or arising from the Company’s various products, or its acts or omissions. In these circumstances, payment may be conditional on the other party making a claim pursuant to the procedures specified in the particular contract. Further, the Company’s obligations under these agreements may be limited in terms of time and/or amount, and in some instances, the Company may have recourse against third parties for certain payments. The terms of such obligations may vary. As of September 30, 2017 and December 31, 2016, no amounts were accrued. (d) Other taxes The Company conducts operations in many tax jurisdictions throughout the United States. In many of these jurisdictions, non-income-based taxes, such as sales and use and telecommunications taxes are assessed on the Company’s operations. Prior to March 2017, the Company had not billed nor collected these taxes from its customers and, in accordance with U.S. GAAP, recorded a provision for its tax exposure in these jurisdictions when it is both probable that a liability has been incurred and the amount of the exposure can be reasonably estimated. Effective March 2017, the Company began collecting these taxes from customers in certain jurisdictions and intends to collect in other jurisdictions in the near term. As a result, the Company recorded a liability of $29.0 million and $28.8 million as of March 31, 2017 and December 31, 2016, respectively. These estimates include several key assumptions including, but not limited to, the taxability of the Company’s services, the jurisdictions in which its management believes it has nexus, and the sourcing of revenues to those jurisdictions. Simultaneously, the Company was and continues to be in discussions with certain states regarding its prior state sales and other taxes, if any, that the Company may owe. During the three months ended June 30, 2017, the Company revised its estimates of its tax exposure based on settlements reached with various states indicating that certain revisions to the key assumptions including, but not limited to, the sourcing of revenue and the taxability of the Company’s services were appropriate in the current period. In the nine months ended September 30, 2017, total impact of these changes on the net loss attributable to common stockholders was a reduction of $13.1 million, or $0.14 per share. As of September 30, 2017, the total liability related to these taxes was $19.4 million. In the event other jurisdictions challenge management’s assumptions and analysis, the actual exposure could differ materially from the current estimates.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity
Stockholders' Equity	11. Stockholders’ Equity (a) Preferred Stock As of September 30, 2017, the Company had authorized 100,000,000 shares of preferred stock, par value $0.001, of which no shares were issued and outstanding. (b) Common Stock As of September 30, 2017 and December 31, 2016, the Company had authorized 1,000,000,000 shares of Class A common stock and 100,000,000 shares of Class B common stock, each par value $0.001 per share. As of September 30, 2017, 68,671,207 shares of Class A common stock and 24,248,777 shares of Class B common stock were issued and outstanding. As of December 31, 2016, 49,996,410 shares of Class A common stock and 37,252,138 shares of Class B common stock were issued and outstanding. The Company had reserved shares of common stock for issuance as follows: As of As of 2017 2016 Stock options issued and outstanding Nonvested restricted stock units issued and outstanding Class A common stock reserved for Twilio.org Stock-based awards available for grant under 2016 Plan Class A common stock reserved for issuance under 2016 ESPP Total

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2017
Stock-Based Compensation
Stock-Based Compensation	12. Stock-Based Compensation 2008 Stock Option Plan The Company granted options under its 2008 Stock Option Plan (the “2008 Plan”), as amended and restated, until June 22, 2016, when the plan was terminated in connection with the Company’s IPO. Accordingly, no shares are available for future issuance under the 2008 Plan. The 2008 Plan continues to govern outstanding equity awards granted thereunder. 2016 Stock Option Plan The Company’s 2016 Stock Option and Incentive Plan (the “2016 Plan”) became effective on June 21, 2016. The 2016 Plan provides for the grant of ISOs, NSOs, restricted stock, RSUs, stock appreciation rights, unrestricted stock awards, performance share awards, dividend equivalent rights and cash-based awards to employees, directors and consultants of the Company. A total of 11,500,000 shares of the Company’s Class A common stock were initially reserved for issuance under the 2016 Plan. These available shares automatically increase each January 1, beginning on January 1, 2017, by 5% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2017, the shares available for grant under the 2016 Plan were automatically increased by 4,362,427 shares. Under the 2016 Plan, the stock options are granted at a price per share not less than 100% of the fair market value per share of the underlying common stock on the date of grant. Under both plans, stock options generally expire 10 years from the date of grant and vest over periods determined by the board of directors. The vesting period for new-hire options and restricted stock units is generally a four-year term from the date of grant, at a rate of 25% after one year, then monthly or quarterly, respectively, on a straight-line basis thereafter. In July 2017, the Company began granting restricted stock units to existing employees that vest in equal quarterly installments over a four year service period. 2016 Employee Stock Purchase Plan The Company’s Employee Stock Purchase Plan (“2016 ESPP”) became effective on June 21, 2016. A total of 2,400,000 shares of the Company’s Class A common stock were initially reserved for issuance under the 2016 ESPP. These available shares automatically increase each January 1, beginning on January 1, 2017, by the lesser of 1,800,000 shares of the common stock, 1% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2017, the shares available for grant under the 2016 Plan were automatically increased by 872,485 shares. The 2016 ESPP allows eligible employees to purchase shares of the Company’s Class A common stock at a discount of up to 15% through payroll deductions of their eligible compensation, subject to any plan limitations. Except for the initial offering period, the 2016 ESPP provides for separate six-month offering periods beginning in May and November of each fiscal year, starting in May 2017. On each purchase date, eligible employees will purchase the Company’s stock at a price per share equal to 85% of the lesser of (i) the fair market value of the Company’s Class A common stock on the offering date or (ii) the fair market value of the Company’s Class A common stock on the purchase date. In the three months ended June 30, 2017, 580,705 shares of the Company’s Class A common stock were purchased under the 2016 ESPP and 224,126 shares are expected to be purchased in the fourth quarter of 2017. As of September 30, 2017, total unrecognized compensation cost related to the 2016 ESPP was $0.3 million, which will be amortized over a weighted-average period of 0.13 years. Stock option activity under the 2008 Plan and the 2016 Plan during the nine months ended September 30, 2017 was as follows: Stock Options Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2016 $ $ Granted Exercised ) Forfeited and cancelled ) Outstanding options as of September 30, 2017 $ $ Options vested and exercisable as of September 30, 2017 $ $ Aggregate intrinsic value represents the difference between the fair value of the Company’s common stock and the exercise price of outstanding “in-the-money” options. Prior to the IPO, the fair value of the Company’s common stock was estimated by the Company’s board of directors. After the IPO, the fair value of the Company’s common stock is the Company’s Class A common stock price as reported on the New York Stock Exchange. The aggregate intrinsic value of stock options exercised was $18.6 million and $119.3 million for the three and nine months ended September 30, 2017, respectively, and $4.4 million and $15.7 million for the three and nine months ended September 30, 2016, respectively. The total estimated grant date fair value of options vested was $3.0 million and $12.2 million for the three and nine months ended September 30, 2017, respectively, and $4.9 million and $11.4 million for the three and nine months ended September 30, 2016, respectively. No options were granted in the three months ended September 30, 2017 and 2016. The weighted-average grant-date fair value of options granted in the nine months ended September 30, 2017 and 2016 was $13.48 and $5.52, respectively. On February 28, 2017, the Company granted a total of 555,000 shares of performance-based stock options in three distinct awards to an employee with grant date fair values of $13.48, $10.26 and $8.41 per share for a total grant value of $5.9 million. The first half of each award vests upon satisfaction of a performance condition and the remainder vests thereafter in equal monthly installments over a 24-month period. The achievement window expires after 4.3 years from the date of grant and the stock options expire seven years after the date of grant. The stock options are amortized over a derived service period of three years, 4.25 years and 4.75 years, respectively. The stock options value and the derived service period were estimated using the Monte-Carlo simulation model. The following table summarizes the details of the performance options: Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2016 — $ — — $ — Granted Exercised — — Forfeited and cancelled — — Outstanding options as of September 30, 2017 $ $ — Options vested and exercisable as of September 30, 2017 — $ — — $ — As of September 30, 2017, total unrecognized compensation cost related to all non-vested stock options was $38.6 million, which will be amortized over a weighted-average period of 2.2 years. Restricted Stock Units Number of Weighted- Aggregate Nonvested RSUs as of December 31, 2016 $ $ Granted Vested ) Forfeited and cancelled ) Nonvested RSUs as of September 30, 2017 $ $ As of September 30, 2017, total unrecognized compensation cost related to nonvested RSUs was $121.1 million, which will be amortized over a weighted-average period of 3.26 years. Equity Awards Granted to Nonemployees In September 2016, the Company granted 30,255 restricted stock units to a nonemployee. The award is vested upon the satisfaction of a service condition over two years starting in August 2015. The stock-based compensation expense recorded for this award during the three and nine months ended September 30, 2017 was $0.1 million and $0.3 million, respectively. As of September 30, 2017, there were no nonemployee awards outstanding. Early Exercises of Nonvested Options As of September 30, 2017 and December 31, 2016, the Company recorded a liability of $0.1 million and $0.3 million for 16,033 and 49,580 unvested shares, respectively, that were early exercised by employees and were subject to repurchase at the respective period end. These amounts are reflected in current and non-current liabilities on the Company’s consolidated balance sheets. Valuation Assumptions The fair value of employee stock options under our equity incentive plans and purchase rights under the ESPP was estimated on the date of grant using the following assumptions in the Black-Scholes option pricing model: Three Months Ended Nine Months Ended 2017 2016 2017 2016 Employee Stock Options: Fair value of common stock * * $24.77 -$31.96 $10.09-$15.00 Expected term (in years) * * Expected volatility * * 46.1%-47.6% 51.4%-53.0% Risk-free interest rate * * 1.9%-2.1% 1.3%-1.5% Dividend rate * * *No stock options were granted in the period. Employee Stock Purchase Plan: Expected term (in years) Expected volatility % % % % Risk-free interest rate % % % % Dividend rate % % % % The following assumptions were used in the Monte Carlo simulation model to estimate the fair value and the derived service period of the performance options: Asset volatility % Equity volatility % Discount rate % Stock price at grant date $ Stock-Based Compensation Expense The Company recorded total stock-based compensation expense as follows (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Cost of revenue $ $ $ $ Research and development Sales and marketing General and administrative Total $ $ $ $

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2017
Net Loss per Share Attributable to Common Stockholders
Net Loss per Share Attributable to Common Stockholders	13. Net Loss per Share Attributable to Common Stockholders Basic and diluted net loss per common share is presented in conformity with the two-class method required for participating securities. Class A and Class B common stock are the only outstanding equity in the Company. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Shares of Class B common stock may be converted into Class A common stock at any time at the option of the stockholder, and are automatically converted into Class A common stock upon sale or transfer, subject to certain limited exceptions. Basic net loss per share attributable to common stockholders is computed using the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed using the weighted-average number of common shares and, if dilutive, potential common shares outstanding during the period. The dilutive effect of these potential common shares is reflected in diluted earnings per share by application of the treasury stock method. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented (in thousands, except share and per share data): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net loss attributable to common stockholders $ ) $ ) $ ) $ ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders Net loss per share attributable to common stockholders, basic and diluted $ ) $ ) $ ) $ ) The following outstanding shares of common stock equivalents were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive: As of September 30, 2017 2016 Issued and outstanding options Nonvested RSUs issued and outstanding Common stock reserved for Twilio.org Shares committed under 2016 ESPP Unvested shares subject to repurchase Total

Transactions with Investors

Transactions with Investors	9 Months Ended
	Sep. 30, 2017
Transactions with Investors
Transactions with Investors	14. Transactions with Investors In 2015, two of the Company’s vendors participated in the Company’s Series E convertible preferred stock financing and owned approximately 1.9% and 1.0%, respectively, of the Company’s outstanding common stock as of September 30, 2017, and 2.0% and 1.0%, respectively, of the Company’s outstanding common stock as of December 31, 2016. The amount of software services the Company purchased from the first vendor was $5.3 million and $14.7 million for the three and nine months ended September 30, 2017, respectively, and $3.7 million and $10.3 million during the three and nine months ended September 30, 2016, respectively. The net amount due to this vendor as of September 30, 2017 was $1.9 million. The amounts due to or from this vendor as of December 31, 2016 were insignificant. The amount of services the Company purchased from the second vendor was $0.2 million and $0.6 million for the three and nine months ended September 30, 2017, respectively, and $0.1 million and $0.3 million for the three and nine months ended September 30, 2016, respectively. The net amounts due from this vendor as of September 30, 2017 and December 31, 2016 were insignificant.

Employee Benefit Plan

Employee Benefit Plan	9 Months Ended
	Sep. 30, 2017
Employee Benefit Plan
Employee Benefit Plan	15. Employee Benefit Plan The Company sponsors a 401(k) defined contribution plan covering all employees. The employer contribution to the plan was $0.3 million and $1.6 million in the three and nine months ended September 30, 2017, respectively, and $0.2 million and $0.9 million in the three and nine months ended September 30, 2016, respectively

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Summary of Significant Accounting Policies
Basis of Presentation	(a) Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in our Annual Report on Form 10-K filed with the SEC on February 21, 2017 (“Annual Report”). The condensed consolidated balance sheet as of December 31, 2016, included herein, was derived from the audited financial statements as of that date, but may not include all disclosures including certain notes required by U.S. GAAP on an annual reporting basis. In the fourth quarter of 2016, the Company adopted the guidance of Accounting Standard Update (“ASU”) No. 2016-09, “Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” , which simplified several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures, statutory tax withholding requirements and classification in the statement of cash flows. The Company adopted all provisions on either prospective or modified retrospective basis. The impact from any of the adopted provisions was immaterial to the Company’s financial position, results of operations and cash flows. Hence, prior periods were not adjusted. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive loss and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2017 or any future period.
Principles of Consolidation	(b) Principles of Consolidation The condensed consolidated financial statements include the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated.
Use of Estimates	(c) Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates are used for, but not limited to, revenue allowances and returns; valuation of the Company’s stock and stock-based awards; recoverability of long-lived and intangible assets; capitalization and useful life of the Company’s capitalized internal-use software; fair value of acquired intangible assets and goodwill; accruals and contingencies. Estimates are based on historical experience and on various assumptions that the Company believes are reasonable under current circumstances. However, future events are subject to change and best estimates and judgments may require further adjustments; therefore, actual results could differ materially from those estimates. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation.
Concentration of Credit Risk	(d) Concentration of Credit Risk Financial instruments that potentially expose the Company to a concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, restricted cash and accounts receivable. The Company maintains cash, cash equivalents, restricted cash and marketable securities with financial institutions that management believes are financially sound and have minimal credit risk exposure. The Company sells its services to a wide variety of customers. If the financial condition or results of operations of any one of the large customers deteriorate substantially, operating results could be adversely affected. To reduce credit risk, management performs ongoing credit evaluations of the financial condition of significant customers. The Company does not require collateral from its credit customers and maintains reserves for estimated credit losses on customer accounts when considered necessary. Actual credit losses may differ from the Company’s estimates. As of September 30, 2017, one customer organization represented approximately 11% of the Company’s gross accounts receivable. As of December 31, 2016, one customer organization represented approximately 16% of the Company’s gross accounts receivable. In the three and nine months ended September 30, 2017, no customers represented more than 10% of the Company’s total revenue. In the three months ended September 30, 2016, one customer organization represented 15% of the Company’s total revenue, and in the nine months ended September 30, 2016, two customer organizations represented 10% and 13% of the Company’s total revenue.
Significant Accounting Policies	(e) Significant Accounting Policies There have been no changes to our significant accounting policies described in our Annual Report.
Recently Issued Accounting Guidance, Not yet Adopted	(f) Recently Issued Accounting Guidance, Not yet Adopted In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Updates (“ASU”) 2017-09, “ Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting” , which clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. The guidance is effective prospectively for interim and annual periods beginning after December 15, 2017 and early adoption is permitted. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In January 2017, the FASB issued ASU 2017-04, “ Simplifying the Test for Goodwill Impairment ”, which removes the second step of the goodwill impairment test that requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. This guidance is effective prospectively for interim and annual reporting periods beginning after December 15, 2019. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In January 2017, the FASB issued ASU 2017-01, “ Business Combinations (Topic 805) Clarifying the Definition of a Business”, which amends the guidance of FASB Accounting Standards Codification Topic 805, “ Business Combinations ”, adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted under certain circumstances. The Company will evaluate the impact of this guidance on its financial statements and related disclosures next time there is a potential business combination. In November 2016, the FASB issued ASU 2016-18, “Restricted Cash” , which requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash and restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted. The Company will adopt this guidance upon its effective date. The restricted cash balances as of September 30, 2017 and December 31, 2016 were $7.4 million and $8.6 million, respectively. In October 2016, the FASB issued ASU 2016-16, “Intra-Entity Transfers Other Than Inventory” , which requires entities to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. This guidance is effective for annual and interim periods beginning after December 15, 2017, and early adoption is permitted. The Company will adopt this guidance upon its effective date. The Company does not expect the adoption of this guidance to have any material impact on the Company’s financial position, results of operations or cash flows. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments” , which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses. ASU 2016-13 is effective for annual and interim periods beginning after December 15, 2019 and early adoption is permitted for annual and interim periods beginning after December 15, 2018. The Company is evaluating the impact of this guidance on its condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, “ Leases” . The standard will affect all entities that lease assets and will require lessees to recognize a lease liability and a right-of-use asset for all leases (except for short-term leases that have a duration of less than one year) as of the date on which the lessor makes the underlying asset available to the lessee. For lessors, accounting for leases is substantially the same as in prior periods. For public companies, the new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. For leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, lessees and lessors must apply a modified retrospective transition approach. While the Company expects the adoption of this standard to result in an increase to the reported assets and liabilities, the Company has not yet determined the full impact that the adoption of this standard will have on its condensed consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, “ Revenue from Contracts with Customers ”. This new guidance will replace most existing U.S. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU 2015-14 which deferred, by one year, the effective date for the new revenue reporting standard for entities reporting under U.S. GAAP. In accordance with the deferral, this guidance will be effective for the Company beginning January 1, 2018 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. In March 2016, the FASB issued ASU 2016-08, “ Revenue from Contracts with Customers, Principal versus Agent Considerations (Reporting Revenue Gross versus Net)” clarifying the implementation guidance on principal versus agent considerations. Specifically, an entity is required to determine whether the nature of a promise is to provide the specified good or service itself (that is, the entity is a principal) or to arrange for the good or service to be provided to the customer by the other party (that is, the entity is an agent). The determination influences the timing and amount of revenue recognition. In April 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing,” clarifying the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments also provide implementation guidance on determining whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time). In May 2016, the FASB issued ASU 2016-12 “Revenue from Contracts with Customers (Topic 606), Narrow-Scope Improvements and Practical Expedients,” which amends the guidance on transition, collectability, noncash consideration and the presentation of sales and other similar taxes. ASU 2016-12 clarifies that, for a contract to be considered completed at transition, all (or substantially all) of the revenue must have been recognized under legacy GAAP. In addition, ASU 2016-12 clarifies how an entity should evaluate the collectability threshold and when an entity can recognize nonrefundable consideration received as revenue if an arrangement does not meet the standard’s contract criteria. In September 2017, the FASB issued ASU 2017-13, “ Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842)” . These amendments provide additional clarification and implementation guidance on the previously issued ASUs. These amendments do not change the core principles of the guidance stated in ASU 2014-09, instead they are intended to clarify and improve operability of certain topics included within the revenue standard. The effective date and transition requirements for ASU 2016-08, ASU 2016-10 and ASU 2016-12 are the same as the effective date and transition requirements for ASU 2014-09. The Company performed its preliminary evaluation and selected a modified retrospective transition method with cumulative effect adjustment as of the standard’s effective date. While the Company has not yet completed the full analysis, based on the evaluation to date, the Company does not expect the adoption of this guidance to have a material impact on its financial position, results of operations or cash flows.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Measurements
Schedule of financial assets by type	The following tables summarize the Company’s financial assets as of September 30, 2017 and December 31, 2016 by type (in thousands): Amortized Cost Net Fair Value Hierarchy as of September 30, 2017 Aggregate Fair Value Losses Level 1 Level 2 Level 3 Value Financial Assets: Cash and cash equivalents: Money market funds $ $ — $ $ — $ — $ Total included in cash and cash equivalents — — — Marketable securities: U.S. Treasury securities ) — — Corporate debt securities ) — — Total marketable securities ) — Total financial assets $ $ ) $ $ $ — $ Carrying Fair Value Hierarchy as of December 31, 2016 Aggregate Fair Value Level 1 Level 2 Level 3 Value Total Financial Assets: Money market funds (included in cash and cash equivalents) $ $ $ — $ — $ Total financial assets $ $ $ — $ — $
Schedule of contractual maturities of marketable securities	The following table summarizes the contractual maturities of marketable securities as of September 30, 2017 (in thousands): Amortized Aggregate Fair Cost Value Financial Assets: Less than one year $ $ One to two years Total $ $

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2017
Property and Equipment
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): As of As of Capitalized software development costs $ $ Leasehold improvements Office equipment Furniture and fixtures Software Total property and equipment Less: accumulated depreciation and amortization ) ) Total property and equipment, net $ $

Recent Acquisition (Tables)

Recent Acquisition (Tables) - Messaging provider based in Sweden	9 Months Ended
	Sep. 30, 2017
Recent Acquisition
Schedule of preliminary purchase price allocation	The following table presents the preliminary purchase price allocation recorded in the Company’s condensed consolidated balance sheet on the acquisition date, and as subsequently adjusted during the three months ended June 30, 2017 (in thousands): Total Net tangible liabilities $ ) Goodwill (1) Intangible assets (2) Total purchase price $ The Company acquired a net deferred tax liability of $2.6 million in this business combination. (1) Goodwill represents the excess of purchase price over the fair value of identifiable tangible and intangible assets acquired and liabilities assumed. The goodwill in this transaction is primarily attributable to the future cash flows to be realized from the acquired technology platform, existing customer and supplier relationships as well as operational synergies. (2) Identifiable finite-lived intangible assets were comprised of the following: Total Estimated Developed technology $ 4 Customer relationships 7-8 Supplier relationships 5 Total intangible assets acquired $
Schedule of identifiable finite-lived intangible assets	Total Estimated Developed technology $ 4 Customer relationships 7-8 Supplier relationships 5 Total intangible assets acquired $

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Intangible Assets
Schedule of goodwill balance	Total Balance as of December 31, 2016 $ Goodwill recorded in connection with the recent acquisition Measurement period adjustment ) Effect of exchange rate Balance as of September 30, 2017 $
Schedule of intangible assets	Intangible assets consisted of the following (in thousands): As of September 30, 2017 Gross Accumulated Net Amortizable intangible assets: Developed technology $ $ ) $ Customer relationships ) Supplier relationships ) Trade name ) — Patent ) Total amortizable intangible assets ) Non-amortizable intangible assets: Domain names — Trademarks — Total $ $ ) $ As of December 31, 2016 Gross Accumulated Net Amortizable intangible assets: Developed technology $ $ ) $ Customer relationships ) Trade name ) Patent ) Total amortizable intangible assets ) Non-amortizable intangible assets: Domain names — Trademarks — Total $ $ ) $
Schedule of total estimated future amortization expense	Total estimated future amortization expense was as follows (in thousands): As of 2017 (remaining 3 months) $ 2018 2019 2020 2021 Thereafter Total $

Accrued Expenses and Other Li26

Accrued Expenses and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Accrued Expenses and Other Liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): As of As of 2017 2016 Accrued payroll and related $ $ Accrued bonus and commission Accrued cost of revenue Sales and other taxes payable ESPP contributions Deferred rent Accrued other expense Total accrued expenses and other current liabilities $ $
Schedule of long-term liabilities	Long-term liabilities consisted of the following (in thousands): As of As of 2017 2016 Deferred rent $ $ Deferred tax liability — Accrued other expense Total other long-term liabilities $ $

Supplemental Balance Sheet In27

Supplemental Balance Sheet Information (Tables)	9 Months Ended
	Sep. 30, 2017
Supplemental Balance Sheet Information
Schedule of the allowance for doubtful accounts	(a) Allowance for doubtful accounts (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Balance, beginning of period $ $ $ $ Additions Write-offs — ) ) ) Balance, end of period $ $ $ $
Schedule of the sales credit reserve	(b) Sales credit reserve (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Balance, beginning of period $ $ $ $ Additions Deductions against reserve ) ) ) ) Balance, end of period $ $ $ $

Revenue by Geographic Area (Tab

Revenue by Geographic Area (Tables)	9 Months Ended
	Sep. 30, 2017
Revenue by Geographic Area
Schedule of revenue by geographic area	The following table sets forth revenue by geographic area (dollars in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Revenue by geographic area: United States $ $ $ $ International Total $ $ $ $ Percentage of revenue by geographic area: United States % % % % International % % % %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies
Schedule of future minimum lease payments under non-cancelable operating leases	Future minimum lease payments under non-cancelable operating leases were as follows (in thousands): Year Ending December 31: As of September 30, 2017 (remaining three months) $ 2018 2019 2020 2021 Thereafter Total minimum lease payments $

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity
Schedule of reserved shares of common stock for issuance	As of As of 2017 2016 Stock options issued and outstanding Nonvested restricted stock units issued and outstanding Class A common stock reserved for Twilio.org Stock-based awards available for grant under 2016 Plan Class A common stock reserved for issuance under 2016 ESPP Total

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Stock-Based Compensation
Schedule of stock option activity	Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2016 $ $ Granted Exercised ) Forfeited and cancelled ) Outstanding options as of September 30, 2017 $ $ Options vested and exercisable as of September 30, 2017 $ $
Schedule of restricted stock unit activity	Number of Weighted- Aggregate Nonvested RSUs as of December 31, 2016 $ $ Granted Vested ) Forfeited and cancelled ) Nonvested RSUs as of September 30, 2017 $ $
Schedule of valuation assumptions for ESPP	Employee Stock Purchase Plan: Expected term (in years) Expected volatility % % % % Risk-free interest rate % % % % Dividend rate % % % %
Schedule of stock based compensation expense	The Company recorded total stock-based compensation expense as follows (in thousands): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Cost of revenue $ $ $ $ Research and development Sales and marketing General and administrative Total $ $ $ $
Employee Stock Option
Stock-Based Compensation
Schedule of valuation assumptions	Three Months Ended Nine Months Ended 2017 2016 2017 2016 Employee Stock Options: Fair value of common stock * * $24.77 -$31.96 $10.09-$15.00 Expected term (in years) * * Expected volatility * * 46.1%-47.6% 51.4%-53.0% Risk-free interest rate * * 1.9%-2.1% 1.3%-1.5% Dividend rate * * *No stock options were granted in the period.
Performance-based stock options
Stock-Based Compensation
Schedule of stock option activity	Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2016 — $ — — $ — Granted Exercised — — Forfeited and cancelled — — Outstanding options as of September 30, 2017 $ $ — Options vested and exercisable as of September 30, 2017 — $ — — $ —
Schedule of valuation assumptions	Asset volatility % Equity volatility % Discount rate % Stock price at grant date $

Net Loss per Share Attributab32

Net Loss per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2017
Net Loss per Share Attributable to Common Stockholders
Schedule of the calculation of basic and diluted net loss per share attributable to common stockholders	The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented (in thousands, except share and per share data): Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net loss attributable to common stockholders $ ) $ ) $ ) $ ) Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders Net loss per share attributable to common stockholders, basic and diluted $ ) $ ) $ ) $ )
Schedule of common stock equivalents excluded from the computation of the diluted net loss per share attributable to common stockholders	As of September 30, 2017 2016 Issued and outstanding options Nonvested RSUs issued and outstanding Common stock reserved for Twilio.org Shares committed under 2016 ESPP Unvested shares subject to repurchase Total

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) - customer	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accounts Receivable | Credit Concentration Risk
Concentration of Credit Risk
Concentration risk (as a percent)			11.00%		16.00%
Number of customers			1		1
Revenue | Customer Concentration Risk
Concentration of Credit Risk
Concentration risk (as a percent)		15.00%
Number of customers	0	1	0	2
Revenue | Customer Concentration Risk | Customer One
Concentration of Credit Risk
Concentration risk (as a percent)				10.00%
Revenue | Customer Concentration Risk | Customer Two
Concentration of Credit Risk
Concentration risk (as a percent)				13.00%

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Restricted Cash
Restricted cash balances	$ 7.4	$ 8.6

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Measurements
Marketable securities, Amortized Cost	$ 192,269
Total marketable securities, Aggregate Fair Value	192,031	$ 0
Recurring
Fair Value Measurements
Marketable securities, Amortized Cost	192,269
Marketable securities, Net Unrealized Losses	(238)
Total financial assets, Amortized Cost or Carrying Value	282,413
Recurring | U.S. Treasury securities
Fair Value Measurements
Marketable securities, Amortized Cost	59,951
Marketable securities, Net Unrealized Losses	(125)
Recurring | Corporate debt securities
Fair Value Measurements
Marketable securities, Amortized Cost	132,318
Marketable securities, Net Unrealized Losses	(113)
Recurring | Carrying Value
Fair Value Measurements
Cash and cash equivalents	90,144
Total financial assets		274,135
Recurring | Carrying Value | Money market funds
Fair Value Measurements
Cash and cash equivalents	90,144	274,135
Recurring | Aggregate Fair Value
Fair Value Measurements
Cash and cash equivalents	90,144
Total marketable securities, Aggregate Fair Value	192,031
Total financial assets	282,175	274,135
Recurring | Aggregate Fair Value | U.S. Treasury securities
Fair Value Measurements
Total marketable securities, Aggregate Fair Value	59,826
Recurring | Aggregate Fair Value | Corporate debt securities
Fair Value Measurements
Total marketable securities, Aggregate Fair Value	132,205
Recurring | Aggregate Fair Value | Money market funds
Fair Value Measurements
Cash and cash equivalents	90,144	274,135
Recurring | Aggregate Fair Value | Level 1
Fair Value Measurements
Cash and cash equivalents	90,144
Total marketable securities, Aggregate Fair Value	59,826
Total financial assets	149,970	274,135
Recurring | Aggregate Fair Value | Level 1 | U.S. Treasury securities
Fair Value Measurements
Total marketable securities, Aggregate Fair Value	59,826
Recurring | Aggregate Fair Value | Level 1 | Money market funds
Fair Value Measurements
Cash and cash equivalents	90,144	$ 274,135
Recurring | Aggregate Fair Value | Level 2
Fair Value Measurements
Total marketable securities, Aggregate Fair Value	132,205
Total financial assets	132,205
Recurring | Aggregate Fair Value | Level 2 | Corporate debt securities
Fair Value Measurements
Total marketable securities, Aggregate Fair Value	$ 132,205

Fair Value Measurements - Contr

Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Measurements
Less than one year, Amortized Cost	$ 121,215
One to two years, Amortized Cost	71,054
Total amortized cost	192,269
Less than one year, Aggregate Fair Value	121,130
One to two years, Aggregate Fair Value	70,901
Total marketable securities, Aggregate Fair Value	$ 192,031	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Disclosures (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Fair Value Measurements
Other-than-temporary impairments	$ 0	$ 0
Interest earned on marketable securities	$ 700	$ 1,800

Property and Equipment - Proper

Property and Equipment - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property and Equipment
Total property and equipment	$ 70,444	$ 50,997
Less: accumulated depreciation and amortization	(22,726)	(13,445)
Total property and equipment, net	47,718	37,552
Capitalized software development costs
Property and Equipment
Total property and equipment	43,571	28,661
Leasehold improvements
Property and Equipment
Total property and equipment	14,208	14,063
Office equipment
Property and Equipment
Total property and equipment	9,263	5,729
Furniture and fixtures
Property and Equipment
Total property and equipment	1,902	1,576
Software
Property and Equipment
Total property and equipment	$ 1,500	$ 968

Property and Equipment - Deprec

Property and Equipment - Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property and Equipment
Depreciation and amortization	$ 3.4	$ 1.9	$ 9.3	$ 4.9

Property and Equipment - Capita

Property and Equipment - Capitalized Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property and Equipment
Capitalized software development costs	$ 5,500	$ 3,400	$ 15,000	$ 9,500
Stock-based compensation capitalized in software development costs	1,200	400	2,712	1,068
Amortization of capitalized software development costs	$ 2,200	$ 1,400	$ 5,900	$ 3,700

Recent Acquisition - Considerat

Recent Acquisition - Consideration (Details) - Messaging provider based in Sweden $ in Millions	Feb. 06, 2017USD ($)
Acquisition
Total purchase price	$ 23
Purchase price paid in cash	23
Amount of purchase price placed into an escrow account	$ 5
Escrow effective period	18 months
Amount deposited into an employee escrow account	$ 2

Recent Acquisition - Purchase P

Recent Acquisition - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Feb. 06, 2017	Dec. 31, 2016
Acquisition
Goodwill	$ 17,407		$ 3,565
Messaging provider based in Sweden
Acquisition
Net tangible liabilities		$ (3,326)
Goodwill		12,588
Intangible assets		13,700
Total purchase price		22,962
Net deferred tax liability		$ 2,600

Recent Acquisition - Identifiab

Recent Acquisition - Identifiable Finite-lived Intangible Assets (Details) - Messaging provider based in Sweden $ in Thousands	Feb. 06, 2017USD ($)
Acquisition
Total intangible assets acquired	$ 13,700
Developed technology
Acquisition
Total intangible assets acquired	$ 5,000
Estimated life (in years)	4 years
Customer relationships
Acquisition
Total intangible assets acquired	$ 6,100
Customer relationships | Minimum
Acquisition
Estimated life (in years)	7 years
Customer relationships | Maximum
Acquisition
Estimated life (in years)	8 years
Supplier relationships
Acquisition
Total intangible assets acquired	$ 2,600
Estimated life (in years)	5 years

Recent Acquisition - Acquisitio

Recent Acquisition - Acquisition Costs (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended	21 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2017
Messaging provider based in Sweden | General and administrative
Business Combinations
Acquisition related costs	$ 0.3	$ 0.4	$ 0.7

Intangible Assets - Goodwill (D

Intangible Assets - Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Goodwill
Balance at the beginning of the period	$ 3,565
Goodwill recorded in connection with the recent acquisition	12,688
Measurement period adjustment	(100)
Effect of exchange rate	1,254
Balance at the end of the period	$ 17,407

Intangible Assets - Amortizable

Intangible Assets - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Intangible Assets
Gross	$ 26,635	$ 11,372
Accumulated Amortization	(5,656)	(1,399)
Net	20,979	9,973
Developed technology
Intangible Assets
Gross	14,888	9,400
Accumulated Amortization	(4,365)	(1,140)
Net	10,523	8,260
Customer relationships
Intangible Assets
Gross	7,096	400
Accumulated Amortization	(774)	(148)
Net	6,322	252
Supplier relationships
Intangible Assets
Gross	2,854
Accumulated Amortization	(364)
Net	2,490
Trade name
Intangible Assets
Gross	60	60
Accumulated Amortization	(60)	(56)
Net		4
Patent
Intangible Assets
Gross	1,737	1,512
Accumulated Amortization	(93)	(55)
Net	$ 1,644	$ 1,457

Intangible Assets - Non-amortiz

Intangible Assets - Non-amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Domain names
Intangible Assets
Non-amortizable intangible assets	$ 32	$ 32
Trademarks
Intangible Assets
Non-amortizable intangible assets	$ 263	$ 263

Intangible Assets - Total Intan

Intangible Assets - Total Intangible Assets, Gross (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets
Amortizable intangible assets, gross	$ 26,635	$ 11,372
Total	26,930	11,667	$ 11,372
Domain names
Intangible Assets
Non-amortizable intangible assets	32	32
Trademarks
Intangible Assets
Non-amortizable intangible assets	$ 263	$ 263

Intangible Assets - Total Int49

Intangible Assets - Total Intangible Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Intangible Assets
Amortizable intangible assets, net	$ 20,979	$ 9,973
Total	21,274	10,268
Domain names
Intangible Assets
Non-amortizable intangible assets	32	32
Trademarks
Intangible Assets
Non-amortizable intangible assets	$ 263	$ 263

Intangible Assets - Total Int50

Intangible Assets - Total Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets
Gross	$ 26,930	$ 11,667	$ 11,372
Accumulated Amortization	(5,656)	(1,399)
Net	$ 21,274	$ 10,268

Intangible Assets - Amortizatio

Intangible Assets - Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Intangible Assets
Amortization expense	$ 1.5	$ 0.1	$ 4.2	$ 0.4

Intangible Assets - Total Estim

Intangible Assets - Total Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Intangible Assets
2017 (remaining 3 months)	$ 2,659
2,018	5,483
2,019	5,081
2,020	2,651
2,021	1,518
Thereafter	3,587
Net	$ 20,979	$ 9,973

Accrued Expenses and Other Li53

Accrued Expenses and Other Liabilities - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Expenses and Other Liabilities
Accrued payroll and related	$ 5,408	$ 3,133
Accrued bonus and commission	3,204	2,251
Accrued cost of revenue	11,553	8,741
Sales and other taxes payable	19,394	28,795
ESPP contributions	3,574	4,364
Deferred rent	668	1,250
Accrued other expense	11,482	10,774
Total accrued expenses and other current liabilities	$ 55,283	$ 59,308

Accrued Expenses and Other Li54

Accrued Expenses and Other Liabilities - Long-term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Expenses and Other Liabilities
Deferred rent	$ 9,335	$ 9,387
Deferred tax liability	2,780
Accrued other expense	434	156
Total long-term liabilities	$ 12,549	$ 9,543

Supplemental Balance Sheet In55

Supplemental Balance Sheet Information - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for doubtful accounts
Balance, beginning of period	$ 923	$ 795	$ 1,076	$ 486
Additions	125	170	407	1,017
Write-offs		(16)	(435)	(554)
Balance, end of period	$ 1,048	$ 949	$ 1,048	$ 949

Supplemental Balance Sheet In56

Supplemental Balance Sheet Information - Sales Credit Reserve (Details) - Sales credit reserve - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Sales credit reserve
Balance, beginning of period	$ 734	$ 652	$ 544	$ 714
Additions	104	169	1,076	1,012
Deductions against reserve	(238)	(337)	(1,020)	(1,242)
Balance, end of period	$ 600	$ 484	$ 600	$ 484

Revenue by Geographic Area - Re

Revenue by Geographic Area - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue by geographic area
Revenue	$ 100,542	$ 71,533	$ 283,784	$ 195,383
United States
Revenue by geographic area
Revenue	76,713	60,535	221,914	165,528
International
Revenue by geographic area
Revenue	$ 23,829	$ 10,998	$ 61,870	$ 29,855

Revenue by Geographic Area - Pe

Revenue by Geographic Area - Percentage of Revenue by Geographic Area (Details) - Revenue - Geographic Concentration Risk	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
United States
Percentage of revenue by geographic area
Percentage of revenue (as a percent)	76.00%	85.00%	78.00%	85.00%
International
Percentage of revenue by geographic area
Percentage of revenue (as a percent)	24.00%	15.00%	22.00%	15.00%

Commitments and Contingencies -

Commitments and Contingencies - Lease Commitments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Lease Commitments
Lease agreements term			7 years
Rent expense	$ 2.1	$ 2.1	$ 6.1	$ 5.1

Commitments and Contingencies60

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2017USD ($)
Future minimum lease payments
2017 (remaining three months)	$ 1,958
2,018	7,326
2,019	7,375
2,020	7,068
2,021	7,033
Thereafter	16,052
Total minimum lease payments	$ 46,812

Commitments and Contingencies61

Commitments and Contingencies - Indemnification Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Indemnification Agreement
Indemnification Agreements
Amount accrued	$ 0	$ 0

Commitments and Contingencies62

Commitments and Contingencies - Other taxes (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Other taxes
Liability for uncertain tax positions	$ 19,400		$ 19,400		$ 29,000	$ 28,800
Net loss attributable to common stockholders	$ (23,453)	$ (11,254)	$ (44,789)	$ (28,716)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)	$ (0.13)	$ (0.49)	$ (0.68)
Change in estimate for non-income-based tax exposure - revisions in key assumptions
Other taxes
Net loss attributable to common stockholders			$ (13,100)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)			$ (0.14)

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred Stock (Details)	Sep. 30, 2017$ / sharesshares
Preferred Stock
Preferred stock, authorized (in shares)	100,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001
Preferred stock, issued (in shares)	0
Preferred stock, outstanding (in shares)	0

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Common Class A
Common Stock
Common stock, authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, issued (in shares)	68,671,207	49,996,410
Common stock, outstanding (in shares)	68,671,207	49,996,410
Common Class B
Common Stock
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, issued (in shares)	24,248,777	37,252,138
Common stock, outstanding (in shares)	24,248,777	37,252,138

Stockholders' Equity - Common65

Stockholders' Equity - Common Stock Shares Reserved (Details) - shares	Sep. 30, 2017	Dec. 31, 2016
Stockholders' Equity
Reserved shares of common stock (in shares)	28,271,590	28,104,671
2016 Stock Option and Incentive Plan
Stockholders' Equity
Stock - based awards available for grant (in shares)	11,601,980	10,143,743
Common Class A
Stockholders' Equity
Common stock reserved for Twilio.org (in shares)	680,397	680,397
Stock Options
Stockholders' Equity
Stock options issued and outstanding (in shares)	11,380,189	14,649,276
Restricted Stock Units (RSUs)
Stockholders' Equity
Nonvested restricted stock units issued and outstanding (in shares)	4,384,898	2,034,217
Employee Stock | Common Class A
Stockholders' Equity
Common stock reserved for issuance under an ESPP (in shares)	224,126	597,038

Stock-Based Compensation - 2008

Stock-Based Compensation - 2008 Stock Option Plan (Details)	Sep. 30, 2017shares
2008 Stock Option Plan
Stock Based Compensation
Shares available for future issuance (in shares)	0

Stock-Based Compensation - 2016

Stock-Based Compensation - 2016 Stock Option Plan (Details) - shares	Jan. 01, 2017	Jul. 31, 2017	Sep. 30, 2017	Jun. 21, 2016
Employee and Nonemployee Stock Options
Stock Based Compensation
Expiration term			10 years
Vesting period			4 years
Employee and Nonemployee Stock Options | First vesting
Stock Based Compensation
Vesting period			1 year
Percentage of vesting rights			25.00%
Restricted Stock Units (RSUs)
Stock Based Compensation
Vesting period			4 years
Restricted Stock Units (RSUs) | Granted in July 2017
Stock Based Compensation
Vesting period		4 years
Restricted Stock Units (RSUs) | First vesting
Stock Based Compensation
Vesting period			1 year
Percentage of vesting rights			25.00%
2016 Stock Option and Incentive Plan
Stock Based Compensation
Maximum automatic annual increase as a percentage of outstanding common shares			5.00%
Automatic increase in shares available for grant (in shares)	4,362,427
2016 Stock Option and Incentive Plan | Common Class A
Stock Based Compensation
Shares reserved for issuance (in shares)				11,500,000
2016 Stock Option and Incentive Plan | Employee and Nonemployee Stock Options
Stock Based Compensation
Minimum grant price as a percentage of fair market value per share of the underlying common stock on the date of grant (as a percent)			100.00%

Stock-Based Compensation - 2068

Stock-Based Compensation - 2016 Employee Stock Purchase Plan (Details) - Employee Stock - USD ($) $ in Millions	Jan. 01, 2017	Dec. 31, 2017	Jun. 30, 2017	Sep. 30, 2017	Jun. 21, 2016
Stock Based Compensation
Maximum automatic annual increase (in shares)				1,800,000
Maximum automatic annual increase as a percentage of outstanding common shares				1.00%
Automatic increase in shares available for grant (in shares)	872,485
Unrecognized compensation cost, other than options				$ 0.3
Weighted-average period (in years)				1 month 17 days
Common Class A
Stock Based Compensation
Shares reserved for issuance (in shares)					2,400,000
Discount from market price, offering date (as a percent)				15.00%
Discount from market price, purchase date (as a percent)				15.00%
Purchase price, percentage of fair market value (as a percent)				85.00%
Shares purchased (in shares)			580,705
Common Class A | Forecast
Stock Based Compensation
Shares purchased (in shares)		224,126

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - Employee and Nonemployee Stock Options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Number of options outstanding
Outstanding options as of the beginning of the period (in shares)			14,649,276
Granted (in shares)	0	0	1,443,335
Exercised (in shares)			(4,615,225)
Forfeited and cancelled (in shares)			(652,197)
Outstanding options as of the end of the period (in shares)	10,825,189		10,825,189	14,649,276
Weighted-average exercise price (per share)
Outstanding options as of the beginning of the period (in dollars per share)			$ 6.14
Granted (in dollars per share)			31.06
Exercised (in dollars per share)			4.88
Forfeited and cancelled (in dollars per share)			7.93
Outstanding options as of the end of the period (in dollars per share)	$ 9.89		$ 9.89	$ 6.14
Weighted-average remaining contractual term and aggregate intrinsic value
Weighted-average remaining contractual term (in years)			7 years 4 months 13 days	7 years 6 months 7 days
Aggregate intrinsic value	$ 218,574		$ 218,574	$ 332,716
Options vested and exercisable and options vested and expected to vest
Options vested and exercisable - number of options outstanding (in shares)	5,166,349		5,166,349
Options vested and exercisable - weighted-average exercise price (in dollars per share)	$ 5.30		$ 5.30
Options vested and exercisable - weighted-average remaining contractual term (in years)			6 years 6 months 15 days
Options vested and exercisable - aggregate intrinsic value	$ 126,828		$ 126,828

Stock-Based Compensation - St70

Stock-Based Compensation - Stock Options - Additional Information (Details) - Employee and Nonemployee Stock Options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock Based Compensation
Aggregate intrinsic value of stock options exercised	$ 18.6	$ 4.4	$ 119.3	$ 15.7
Grant date fair value of options vested	$ 3	$ 4.9	$ 12.2	$ 11.4
Weighted-average grant date fair value of options granted (in dollars per share)			$ 13.48	$ 5.52

Stock-Based Compensation - Perf

Stock-Based Compensation - Performance-Based Stock Options (Details) $ / shares in Units, $ in Millions	Feb. 28, 2017USD ($)item$ / shares	Sep. 30, 2017$ / sharesshares
Performance-based stock options
Stock-Based Compensation
Number of distinct awards | item	3
Total grant value | $	$ 5.9
Vesting period upon satisfaction of performance condition	24 months
Performance condition achievement window	4 years 3 months 18 days
Expiration term	7 years
Number of options outstanding
Granted (in shares) | shares		555,000
Outstanding options as of the end of the period (in shares) | shares		555,000
Weighted-average exercise price (per share)
Granted (in dollars per share)		$ 31.72
Outstanding options as of the end of the period (in dollars per share)		$ 31.72
Weighted-average remaining contractual term and aggregate intrinsic value
Weighted-average remaining contractual term (in years)		6 years 4 months 28 days
Performance-based stock options, $13.48 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 13.48
Derived service period	3 years
Performance-based stock options, $10.26 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 10.26
Derived service period	4 years 3 months
Performance-based stock options, $8.41 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 8.41
Derived service period	4 years 9 months

Stock-Based Compensation - St72

Stock-Based Compensation - Stock Options - Unrecognized Compensation Cost (Details) - Employee and Nonemployee Stock Options $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Stock Based Compensation
Unrecognized compensation cost, options	$ 38.6
Weighted-average period (in years)	2 years 2 months 12 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Number of units outstanding
Nonvested RSUs at the beginning of the period (in shares)	2,034,217
Granted (in shares)	3,093,326
Vested (in shares)	(492,757)
Forfeited and cancelled (in shares)	(249,888)
Nonvested RSUs at the end of the period (in shares)	4,384,898
Weighted-average grant date fair value (per share)
Nonvested RSUs (in dollars per share)	$ 30.86	$ 32.66
Aggregate intrinsic value
Aggregate intrinsic value	$ 130,818	$ 58,687

Stock-Based Compensation - Re74

Stock-Based Compensation - Restricted Stock Units - Unrecognized Compensation Cost (Details) - Restricted Stock Units (RSUs) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Stock Based Compensation
Unrecognized compensation cost, other than options	$ 121.1
Weighted-average period (in years)	3 years 3 months 4 days

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Awards Granted to Nonemployees (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock Based Compensation
Stock-based compensation expense		$ 14,188	$ 7,648	$ 35,973	$ 15,649
Nonemployee Restricted Stock Units
Stock Based Compensation
Restricted stock units granted (in shares)	30,255
Service condition period (in years)	2 years
Stock-based compensation expense		$ 100		$ 300
Restricted stock unit awards outstanding (in shares)		0		0
Nonemployee Stock Option
Stock Based Compensation
Stock option awards outstanding (in shares)		0		0

Stock-Based Compensation - Earl

Stock-Based Compensation - Early Exercises of Nonvested Options (Details) - Employee Stock Option - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Stock Based Compensation
Liability for unvested shares	$ 0.1	$ 0.3
Unvested shares that were early exercised (in shares)	16,033	49,580

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Stock Option
Valuation Assumptions
Expected term (in years)			6 years 29 days	6 years 29 days
Expected volatility, low end of range (as a percent)			46.10%	51.40%
Expected volatility, high end of range (as a percent)			47.60%	53.00%
Risk-free interest rate, low end of range (as a percent)			1.90%	1.30%
Risk-free interest rate, high end of range (as a percent)			2.10%	1.50%
Dividend rate (as a percent)			0.00%	0.00%
Stock options granted (in shares)	0	0
Employee Stock
Valuation Assumptions
Expected term (in years)	6 months	10 months 24 days	6 months	10 months 24 days
Expected volatility (as a percent)	33.20%	52.00%	33.20%	52.00%
Risk-free interest rate (as a percent)	1.10%	0.60%	1.10%	0.60%
Dividend rate (as a percent)	0.00%	0.00%	0.00%	0.00%
Performance-based stock options
Valuation Assumptions
Stock options granted (in shares)			555,000
Asset volatility (as a percent)			40.00%
Equity volatility (as a percent)			45.00%
Discount rate (as a percent)			14.00%
Stock price at grant date (in dollars per share)	$ 31.72		$ 31.72
Minimum | Employee Stock Option
Valuation Assumptions
Fair value of common stock (in dollars per share)			24.77	$ 10.09
Maximum | Employee Stock Option
Valuation Assumptions
Fair value of common stock (in dollars per share)			$ 31.96	$ 15

Stock-Based Compensation - St78

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock-Based Compensation Expense
Stock-based compensation expense	$ 14,188	$ 7,648	$ 35,973	$ 15,649
Cost of revenue
Stock-Based Compensation Expense
Stock-based compensation expense	180	84	460	135
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense	6,493	3,741	16,687	7,636
Sales and marketing
Stock-Based Compensation Expense
Stock-based compensation expense	2,603	1,432	6,961	3,282
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense	$ 4,912	$ 2,391	$ 11,865	$ 4,596

Net Loss per Share Attributab79

Net Loss per Share Attributable to Common Stockholders - General Information (Details)	Sep. 30, 2017Vote
Common Class A
Net Loss Per Share Attributable to Common Stockholders
Votes per share	1
Common Class B
Net Loss Per Share Attributable to Common Stockholders
Votes per share	10

Net Loss per Share Attributab80

Net Loss per Share Attributable to Common Stockholders - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Loss Per Share Attributable to Common Stockholders
Net loss attributable to common stockholders	$ (23,453)	$ (11,254)	$ (44,789)	$ (28,716)
Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders (in shares)	92,156,768	83,887,901	90,543,087	42,030,989
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)	$ (0.13)	$ (0.49)	$ (0.68)

Net Loss per Share Attributab81

Net Loss per Share Attributable to Common Stockholders - Anti-Dilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Anti-dilutive securities
Total	16,685,643	19,576,064
Employee and Nonemployee Stock Options
Anti-dilutive securities
Total	11,380,189	16,476,973
Restricted Stock Units (RSUs)
Anti-dilutive securities
Total	4,384,898	1,639,378
Common stock reserved for Twilio.org
Anti-dilutive securities
Total	680,397	780,397
Employee Stock
Anti-dilutive securities
Total	224,126	604,865
Unvested shares subject to repurchase
Anti-dilutive securities
Total	16,033	74,451

Transactions with Investors (De

Transactions with Investors (Details) - Investor $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)Counterparty	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)Counterparty	Sep. 30, 2016USD ($)	Dec. 31, 2016Counterparty	Dec. 31, 2015Counterparty
Transactions With Investors
Vendors, number | Counterparty	2		2		2	2
Vendor 1
Transactions With Investors
Ownership percentage (as a percent)	1.90%		1.90%		2.00%
Purchases from vendor	$ 5.3	$ 3.7	$ 14.7	$ 10.3
Amount due from vendor	$ 1.9		$ 1.9
Vendor 2
Transactions With Investors
Ownership percentage (as a percent)	1.00%		1.00%		1.00%
Purchases from vendor	$ 0.2	$ 0.1	$ 0.6	$ 0.3

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Benefit Plan
Employer contributions	$ 0.3	$ 0.2	$ 1.6	$ 0.9