Free Color Contrast Checker that works offline
Compare two colors, preview sample text and see whether the combination meets common WCAG contrast thresholds.
What this color contrast checker does
The ratio is calculated from relative luminance after converting sRGB channels to linear light. Results are shown for normal text, large text and non-text UI guidance.
How to use the Color Contrast Checker
- Paste or enter foreground and background colors.
- Adjust the available options for the result you need.
- Choose Check contrast and review the output before using it.
- Copy or download the result, then clear the page if the input was sensitive.
Common uses
- Preparing accessible color combinations for development and testing
- Inspecting copied data without sending it to a remote service
- Creating reusable examples for documentation or local projects
- Completing a browser-based workflow while offline
Private processing and offline access
This tool does not submit your input to a conversion server. Processing takes place inside the browser using local JavaScript and standard Web APIs. After the PWA has been installed or cached, the page and its core features remain available without an internet connection. Closing or clearing the page removes unsaved input; the tool does not create an account or cloud history.
Tips for accurate results
- Review generated output before deploying it to production.
- Keep a copy of important source data before transforming it.
- This tool runs locally, but your browser extensions and device security still matter.
Frequently asked questions
Does this tool upload my data?
No. Color Contrast Checker processes its input in the current browser.
Can it work offline?
Yes. After the PWA has cached this page and its supporting files, the core tool works without an internet connection.
Should I review the result?
Yes. Generated configuration and formatted code should be reviewed before it is used in a production system.