v3.25.2
Cover - shares
 6 Months Ended
Jun. 30, 2025
Aug. 01, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-40693  
Entity Registrant Name RALLYBIO CORPORATION  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 85-1083789  
Entity Address, Address Line One 234 Church Street  
Entity Address, Address Line Two Suite 1020  
Entity Address, City or Town New Haven  
Entity Address, State or Province CT  
Entity Address, Postal Zip Code 06510  
City Area Code 203  
Local Phone Number 859-3820  
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Trading Symbol RLYB  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Bankruptcy Proceedings, Reporting Current true  
Entity Common Stock, Shares Outstanding (in shares)   41,786,471
Entity Central Index Key 0001739410  
Document Fiscal Year Focus 2025  
Current Fiscal Year End Date --12-31  
Document Fiscal Period Focus Q2  
Amendment Flag false