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Ratio vs Contrast Ratio: catalog facts
Ratio	Contrast Ratio
Free Free and open source under GPL-3.0-or-later.	Free Free to use in the browser.
macOS, Linux	Web
Checks text and non-text contrast criteria Supports a focus appearance criterion	Updates the ratio live as you type Handles semi-transparent colors with an error margin
Focused on WCAG criteria 1.4.3, 1.4.11, and 2.4.13	Checks one color pair at a time The hosting page includes marketing content from Siege Media
Downloadable app	Web application
Open source	Closed source
License: GPL-3.0-or-later	License not stated
No account needed	No account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 8, 2026	Official website Full listing and sources Checked September 23, 2026

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