| Document And Entity Information | Aug. 09, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 9, 2021 |
| Entity Registrant Name | Kodiak Sciences Inc. |
| Entity Central Index Key | 0001468748 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-38682 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 27-0476525 |
| Entity Address, Address Line One | 1200 PAGE MILL RD |
| Entity Address, City or Town | PALO ALTO |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94304 |
| City Area Code | 650 |
| Local Phone Number | 281-0850 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.0001 |
| Trading Symbol | KOD |
| Security Exchange Name | NASDAQ |
