v3.25.1
Cover - shares
3 Months Ended
Mar. 31, 2025
Apr. 21, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 001-35662  
Entity Registrant Name QUALYS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 77-0534145  
Entity Address, Address Line One 919 E. Hillsdale Boulevard, 4th Floor  
Entity Address, City or Town Foster City  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94404  
City Area Code 650  
Local Phone Number 801-6100  
Title of 12(b) Security Common stock, $0.001 par value per share  
Trading Symbol QLYS  
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 Common Stock, Shares Outstanding   36,326,126
Entity Central Index Key 0001107843  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Amendment Flag false