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Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator.
WCAG Contrast Checker is a free, browser-based design tool. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator.
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Color Name FinderFind the nearest CSS named color for any hex or RGB value — see the top 5 closes Color MixerMix two colors together at any ratio — see the blended result as hex, RGB, and a Gradient Text GeneratorCreate stunning CSS gradient text — pick colors, direction, and preview your tex Neumorphism CSS GeneratorGenerate CSS neumorphism (soft UI) effects with real-time preview — adjust colorWCAG 2.1 success criterion 1.4.3 requires a minimum contrast ratio of 4.5:1 between text and background for normal text, and 3:1 for large text (18pt+ or 14pt+ bold). The 2.2 update keeps those thresholds and adds focus-indicator requirements under 2.4.11. FastTool's color contrast checker computes the exact ratio for any two colors using the sRGB relative luminance formula defined in the W3C spec, flags whether you pass AA, AA Large, AAA, or none, and previews the pairing on live sample text so you can see the problem instead of arguing about it. Everything runs in the browser — no design system tokens are uploaded anywhere.
Accessibility is a legal requirement in the EU (EAA, in force June 2025), in the US (ADA Title III case law, Section 508), and in virtually every public-sector procurement process worldwide. But it is also the single cheapest usability win a product team can make: readable text helps every user, not just those with low vision, and the fix is almost always a one-line color change. The checker removes the guesswork from that change.
text-muted gray-on-white combination renders at 3.9:1 — just below AA. Nudging the gray two steps darker in Figma brings it to 4.7:1 and the change propagates through every downstream product with a single token update.2.1:1 against the button background — a fail even for large text. Switching the label to white lifts it to 8.2:1 without touching the brand palette.The contrast ratio is (L1 + 0.05) / (L2 + 0.05), where L1 and L2 are the relative luminances of the lighter and darker colors. Relative luminance is computed from sRGB channels by first undoing the gamma encoding (c / 12.92 for low values, ((c + 0.055) / 1.055)^2.4 for high values) and then applying the 0.2126 R + 0.7152 G + 0.0722 B weighting that reflects human photopic sensitivity. The result is a unitless ratio between 1:1 (identical colors) and 21:1 (pure black on pure white). Note that WCAG 3.0's APCA proposal uses a different, perceptually-weighted algorithm; the checker also reports the APCA Lc value for forward compatibility, but the canonical pass/fail answer for most compliance conversations is still the 2.x ratio.
Test your colors against your actual background, not against pure white. A gray card on a white page has a different effective contrast than the same text on pure #ffffff, and the difference is enough to flip an AA pass into a fail. Use the checker on the real rendered pixels, not the design token.
Artifacts emitted by this tool are ready to drop directly into production codebases — no post-processing required. The output targets evergreen browsers released within the last two years and degrades gracefully on older ones where the CSS spec defines a fallback. Where platforms diverge on newer features, the tool favours the broadly-supported form unless you explicitly opt into a newer-only output.
WCAG Contrast Checker is a free, browser-based utility in the Design category. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. Standard processing runs on the client — no account is required, and there is no paywall or usage cap. The implementation uses audited standard-library primitives and published specifications rather than proprietary algorithms, so the output is reproducible and transparent.
FastTool targets WCAG 2.2 Level AA conformance: keyboard-navigable controls, visible focus states, semantic HTML, sufficient colour contrast, and screen-reader compatibility. If you encounter an accessibility issue, please reach us via the site footer.
Whether you are a beginner or an expert, WCAG Contrast Checker makes it easy to advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator in seconds. In the fast-paced world of digital design, being able to advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator without opening a separate application keeps your creative momentum going. Just enter your data and WCAG Contrast Checker gives you results instantly. From there you can preview, copy, or export the result. Features such as WCAG 2.1 contrast ratio calculation and AA and AAA pass/fail badges for normal and large text are integrated directly into WCAG Contrast Checker, so you do not need separate tools for each step. Access WCAG Contrast Checker from any device with a web browser — the layout adjusts automatically to your screen size. No app download required, and your results are identical regardless of the platform you use. Standard input stays on your device — WCAG Contrast Checker uses client-side JavaScript for core processing, keeping the workflow private without requiring an account. Because there is no account, no setup, and no learning curve, WCAG Contrast Checker fits into any workflow naturally. Open the page, get your result, and move on to what matters next. Start using WCAG Contrast Checker today and speed up your design process without spending a dime.
You might also like our Contrast Ratio Checker. Check out our Color Blindness Simulator. For related tasks, try our Gradient Text Generator.
WCAG AA requires 4.5:1 for normal text and 3:1 for large text. 12.63:1 is excellent contrast — easily readable.
Light gray on white is a common accessibility mistake. At 2.85:1, it fails AA for body text — use #767676 or darker.
| Feature | Browser-Based (FastTool) | Design Suite | Mobile Design App |
|---|---|---|---|
| Cost | Free, no limits | $$$ license or subscription | Free with limitations |
| Privacy | Browser-local standard processing | Local processing | May upload data |
| Installation | None — runs in browser | Large download + install | Browser extension install |
| Speed | Instant for quick tasks | Powerful for complex work | Lightweight but limited |
| Cross-Platform | Works everywhere | OS-specific versions | Browser-dependent |
| Updates | Always latest version | Manual updates needed | Auto-updates |
No tool is perfect for every scenario. Here are situations where a different approach will serve you better:
The WCAG (Web Content Accessibility Guidelines) color contrast requirements specify minimum contrast ratios between foreground text and background colors. Level AA requires 4.5:1 for normal text (under 18pt or 14pt bold) and 3:1 for large text (18pt+ or 14pt+ bold). Level AAA requires 7:1 for normal text and 4.5:1 for large text. The contrast ratio is calculated from the relative luminance of each color using the formula (L1 + 0.05) / (L2 + 0.05), where L1 is the lighter color's luminance and L2 is the darker's. Relative luminance accounts for the human eye's different sensitivity to red, green, and blue light.
Common contrast failures include light gray text on white backgrounds (popular for aesthetic minimalism but often below 4.5:1), colored text on colored backgrounds (where both colors have similar luminance despite different hues), and text overlaying images (where contrast varies across the image). Placeholder text in form fields is a frequent offender. Solutions include darkening text colors, adding text shadows or semi-transparent overlays on images, and testing all interactive states (default, hover, focus, disabled). The draft WCAG 3.0 proposes replacing the current contrast algorithm with APCA (Accessible Perceptual Contrast Algorithm), which better accounts for font size, weight, and spatial frequency effects on readability.
Built with CSS and JavaScript, WCAG Contrast Checker processes design parameters using mathematically precise algorithms with capabilities including WCAG 2.1 contrast ratio calculation, AA and AAA pass/fail badges for normal and large text, live text preview on colored background. The tool uses the browser's built-in color parsing for accuracy and generates output compatible with all modern CSS specifications. Visual previews are rendered using the same engine that displays websites, so what you see matches what your users will see. All calculations happen instantly in your browser with no server roundtrip.
Web Content Accessibility Guidelines (WCAG) require a minimum contrast ratio of 4.5:1 for normal text to ensure readability for people with low vision.
The RGB color model used in digital displays was developed based on the three types of cone cells in the human eye: red, green, and blue sensitive.
Part of the FastTool collection, WCAG Contrast Checker is a zero-cost design tool that works in any modern browser. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. Capabilities like WCAG 2.1 contrast ratio calculation, AA and AAA pass/fail badges for normal and large text, live text preview on colored background are available out of the box. Because it uses client-side JavaScript, standard input can be processed without a FastTool application server.
As a browser-based design tool, WCAG Contrast Checker addresses this by letting you choose your design settings and get results instantly. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. It is free, private, and works on any device with a modern web browser. Tool input is handled locally where browser APIs support it, and FastTool does not require uploads for standard use.
Check out: Contrast Ratio Checker
Difference between AA and AAA is central to what WCAG Contrast Checker does. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. With WCAG Contrast Checker on FastTool, you can work with difference between AA and AAA using WCAG 2.1 contrast ratio calculation, AA and AAA pass/fail badges for normal and large text, live text preview on colored background, all running client-side in your browser. No account creation or software installation needed — results appear instantly.
WCAG Contrast Checker makes it easy to How does color blindness simulation work. Open the tool, choose your design settings, configure options such as WCAG 2.1 contrast ratio calculation, AA and AAA pass/fail badges for normal and large text, live text preview on colored background, and get your result immediately. Everything is processed client-side in your browser for maximum speed and privacy.
You might also find useful: Color Blindness Simulator
As a browser-based design tool, WCAG Contrast Checker addresses this by letting you choose your design settings and get results instantly. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. It is free, private, and works on any device with a modern web browser. Tool input is handled locally where browser APIs support it, and FastTool does not require uploads for standard use.
WCAG Contrast Checker is a browser-based design tool that anyone can use for free. Advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. It is especially useful for designers and creatives working on web design, graphic design, and creative projects. The tool offers WCAG 2.1 contrast ratio calculation, AA and AAA pass/fail badges for normal and large text, live text preview on colored background and processes everything locally on your device.
Check out: Color Picker
Yes. WCAG Contrast Checker runs primarily in your browser, so standard inputs stay on your device. FastTool does not intentionally upload or log tool input for this workflow. This client-side approach is ideal for design work that involves private or confidential information. Even if you are on a corporate network with strict data policies, using WCAG Contrast Checker does not send tool input to a FastTool application server.
Yes. WCAG Contrast Checker is fully responsive and works on iOS, Android, and any device with a modern web browser. The layout adapts automatically to your screen size, and all features work exactly the same as on a desktop computer. Buttons and input fields are sized for touch interaction, so the experience feels natural on a phone. You can even tap the share button in your mobile browser and choose Add to Home Screen for instant, app-like access.
You might also find useful: Color Converter (HEX/RGB/HSL/HSV/CMYK)
Once the page finishes loading, WCAG Contrast Checker works without an internet connection. All computation runs locally in your browser using JavaScript, so there are no server requests during normal operation. Feel free to disconnect after the initial load — your workflow will not be affected. Bookmark the page so you can reach it quickly the next time you are online, and the tool will be ready to use again as soon as the page loads.
Three things set WCAG Contrast Checker apart: it is free with no limits, it keeps standard processing in the browser, and it works on any device without installation. Most competing tools require accounts, charge for advanced features, or require project uploads for processing. WCAG Contrast Checker avoids all three of these issues by running everything client-side. Additionally, the interface is available in 21 languages and works offline after the initial page load, which most alternatives do not offer.
Check out: CSS Gradient Generator
Use WCAG Contrast Checker when designing websites to quickly advanced WCAG 2.1 contrast checker with AA/AAA pass/fail badges, color blindness simulation, auto-fix suggestions, live text preview, and random accessible palette generator. without switching between applications. The zero-cost, zero-setup nature of WCAG Contrast Checker makes it ideal for this scenario — you get professional-quality results without committing to a software purchase or subscription.
Apply WCAG Contrast Checker during brand identity projects where consistent design values need to be generated or verified across deliverables. The instant results and copy-to-clipboard functionality make this workflow fast and efficient, letting you move from task to finished output in a matter of seconds.
During rapid prototyping, WCAG Contrast Checker lets you iterate on design decisions faster by giving you instant feedback in the browser. This is a scenario where having a reliable, always-available tool in your browser saves meaningful time compared to launching a desktop application or searching for an alternative.
Prepare design assets for client presentations using WCAG Contrast Checker — generate values on the spot during meetings. Because WCAG Contrast Checker runs entirely in your browser, you maintain full control over your data throughout the process, which is especially important when working with sensitive or proprietary information.
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