Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 31, 2019
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Trading Symbol KOD  
Entity Registrant Name Kodiak Sciences Inc.  
Entity Central Index Key 0001468748  
Entity Current Reporting Status Yes  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Shell Company false  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Common Stock, Shares Outstanding   36,931,141
Entity File Number 001-38682  
Entity Tax Identification Number 270476525  
Entity Address, Address Line One 2631 Hanover Street  
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