| Cover Page | May 05, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | May 5, 2021 |
| Entity Registrant Name | CAREDX, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36536 |
| Entity Tax Identification Number | 94-3316839 |
| Entity Address, Address Line One | 1 Tower Place, |
| Entity Address, Address Line Two | 9th Floor |
| Entity Address, City or Town | South San Francisco, |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94080 |
| City Area Code | 415 |
| Local Phone Number | 287-2300 |
| 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 |
| Trading Symbol | CDNA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001217234 |
| Amendment Flag | false |
