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Contrast Ratio vs Kontrast: catalog facts
Contrast Ratio	Kontrast
Free Free to use in the browser.	Free Free and open source under GPL-3.0-or-later.
Web	Linux
Updates the ratio live as you type Handles semi-transparent colors with an error margin	Checks color combinations for readability and accessibility Available through Flathub and Linux package managers
Checks one color pair at a time The hosting page includes marketing content from Siege Media	Linux only
Web application	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0-or-later
No account needed	Not stated if an account is 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 October 8, 2026

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