| Document and Entity Information | Dec. 22, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 22, 2020 |
| Entity Registrant Name | THE TRADE DESK, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-37879 |
| Entity Tax Identification Number | 27-1887399 |
| Entity Address, Address Line One | 42 N. Chestnut Street |
| Entity Address, City or Town | Ventura |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 93001 |
| City Area Code | 805 |
| Local Phone Number | 585-3434 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001671933 |
| Title of 12(b) Security | Class A Common Stock, par value $0.000001 per |
| Trading Symbol | TTD |
| Security Exchange Name | NASDAQ |
