| Cover page Document | Feb. 02, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 2, 2021 |
| Entity Registrant Name | ALPHABET INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-37580 |
| Entity Tax Identification Number | 61-1767919 |
| Entity Address, Address Line One | 1600 Amphitheatre Parkway |
| Entity Address, City or Town | Mountain View |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94043 |
| City Area Code | 650 |
| Local Phone Number | 253-0000 |
| 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 | 0001652044 |
| Amendment Flag | false |
| Common Class A | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Class A Common Stock, $0.001 par value |
| Trading Symbol | GOOGL |
| Security Exchange Name | NASDAQ |
| Capital Class C | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Class C Capital Stock, $0.001 par value |
| Trading Symbol | GOOG |
| Security Exchange Name | NASDAQ |
