| Document and Entity Information Document | Nov. 07, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Nov. 7, 2019 |
| Entity Registrant Name | DROPBOX, INC. |
| Entity Central Index Key | 0001467623 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38434 |
| Entity Tax Identification Number | 26-0138832 |
| Entity Address, Address Line One | 1800 Owens St. |
| Entity Address, City or Town | San Francisco |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94158 |
| City Area Code | 415 |
| Local Phone Number | 857-6800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, par value $0.00001 per share |
| Trading Symbol | DBX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
