v3.25.4
Cover - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2025
Mar. 06, 2026
Jun. 30, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-42045    
Registrant Name GRAIL, Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 86-3673636    
Entity Address, Address Line One 1525 O’Brien Drive    
Entity Address, City or Town Menlo Park    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 94025    
City Area Code 833    
Local Phone Number 694-2553    
Title of 12(b) Security Common Stock, $0.001 par value    
Trading Symbol GRAL    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
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 true    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 1.9
Entity Common Stock, Shares Outstanding   41,020,255  
Documents Incorporated by Reference
Portions of the registrant’s definitive Proxy Statement relating to its 2026 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. Such definitive Proxy Statement will be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2025.
    
Central Index Key 0001699031    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false