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WebAIM Contrast Checker vs WhoCanUse: catalog facts
WebAIM Contrast Checker	WhoCanUse
Free Free to use.	Free Free to use; the developer accepts GitHub sponsorships.
Web	Web
Separate results for normal text, large text and UI components Alpha and lightness controls for adjusting colors	Previews each color blindness type and other vision conditions Shows share of people affected by each condition
Checks one color pair at a time Does not scan a live page	Checks one color pair at a time Does not scan a live web page
Web application	Web application
Closed source	Closed source
License not stated	License not stated
No account needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.