| Document and Entity Information Document | Jan. 10, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 10, 2022 |
| Entity Registrant Name | Redfin Corporation |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38160 |
| Entity Tax Identification Number | 74-3064240 |
| Entity Address, Address Line One | 1099 Stewart Street, Suite 600 |
| Entity Address, City or Town | Seattle |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98101 |
| City Area Code | (206) |
| Local Phone Number | 576-8333 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.001 par value per share |
| Trading Symbol | RDFN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001382821 |
| Amendment Flag | false |
