v3.25.2
Cover - shares
 6 Months Ended
Jun. 30, 2025
Aug. 01, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-39303  
Entity Registrant Name PLIANT THERAPEUTICS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 47-4272481  
Entity Address, Address Line One 331 Oyster Point Blvd.  
Entity Address, City or Town South San Francisco,  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94080  
City Area Code 650  
Local Phone Number 481-6770  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   61,388,154
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0001746473  
Current Fiscal Year End Date --12-31  
Common Stock, par value $0.0001 per share    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Trading Symbol PLRX  
Security Exchange Name NASDAQ  
Series A Junior Participating Preferred Purchase Rights    
Document Information [Line Items]    
Title of 12(b) Security Series A Junior Participating Preferred Purchase Rights  
No Trading Symbol Flag true  
Security Exchange Name NASDAQ