v3.26.3
Cover Page - shares
 9 Months Ended
Sep. 30, 2026
Nov. 03, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2026  
Document Transition Report false  
Entity File Number 001-40653  
Entity Registrant Name Duolingo, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 45-3055872  
Entity Address, Address Line One 141 S St Clair Street,  
Entity Address, Address Line Two Suite 501  
Entity Address, City or Town Pittsburgh  
Entity Address, State or Province PA  
Entity Address, Postal Zip Code 15206  
City Area Code 412  
Local Phone Number 567-6602  
Title of 12(b) Security Class A common stock, par value $0.0001 per share  
Trading Symbol DUOL  
Security Exchange Name NASDAQ  
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 Central Index Key 0001562088  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Common Class A    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   40,779,003
Common Class B    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   6,399,257