Free Website Accessibility Tool
Color Blind Website Checker
Analyze any website and visualize how color blind users experience your UI. Identify accessibility issues and ensure inclusive design.
Enter Website URL
✓ Live Screenshot: Uses headless browser to capture any website automatically.
Upload Website Screenshot
Drag and drop a screenshot here, or click to browse
Supports JPG, PNG, GIF, WebP (max 10MB)
What is a Color Blind Website Checker?
A color blind website checker is an essential accessibility tool that reveals how your website appears to users with various forms of color vision deficiency. Unlike simple contrast checkers, this tool transforms your entire website interface to replicate the actual visual experience of colorblind users—showing you exactly which elements become confusing, invisible, or misleading when certain colors can't be perceived.
For web designers and developers, this tool bridges a critical gap in the design process. You might create a beautiful interface with careful color choices that work perfectly for typical color vision, but 8% of males and 0.5% of females worldwide have some form of color blindness. Without testing, you're potentially creating barriers for millions of users who experience your UI differently than you intended.
The checker works by applying scientifically-validated color transformation algorithms to screenshots of your website. These transformations simulate the reduced color discrimination that occurs when specific cone cells in the retina are absent or dysfunctional. By viewing your design through these simulations, you identify real accessibility problems before users encounter them.
Why Designers Use This Tool
Professional designers and development teams integrate color blindness testing into their workflows for several strategic reasons. First, it's a requirement for WCAG 2.1 Level AA compliance—many organizations, government websites, and e-commerce platforms must demonstrate accessibility. Using a website checker provides documentation and evidence of due diligence in accessibility testing.
Beyond compliance, there's a compelling business case. When your SaaS dashboard uses red and green to indicate success and failure states, users with deuteranopia (the most common form) literally cannot distinguish between them. That's not just bad UX—it's a barrier preventing users from completing tasks. E-commerce sites with color-coded product attributes or availability indicators lose sales when those indicators become meaningless to colorblind shoppers.
This tool is particularly valuable for complex web applications: data dashboards with multi-colored charts, admin panels with status indicators, form validation that relies on red/green messages, navigation systems with color-coded categories, and mobile app previews where small touch targets need clear visual distinction. Testing these interfaces early prevents expensive redesigns later.
Color Blindness Types You Can Test
Protanopia & Protanomaly
Red color blindness
Missing or defective red cones. Reds appear darker and brownish, and red-green distinctions fail. Affects ~1% of males. Critical for testing error messages and status indicators.
Deuteranopia & Deuteranomaly
Green color blindness
Missing or defective green cones. Most common type (~6% of males). Greens and reds look similar. Essential to test for navigation, buttons, and data visualizations.
Tritanopia & Tritanomaly
Blue-yellow color blindness
Missing or defective blue cones. Very rare (0.01% of population). Blues and yellows become confused. Important for branding and accent color testing.
Achromatopsia
Complete color blindness
No functional cone cells—vision in grayscale only. Extremely rare but important for testing whether your UI remains functional without any color information.
Achromatomaly
Blue cone monochromacy
Only blue cones function. Severe color vision reduction with very limited color perception. Helps ensure interfaces work with minimal color cues.
Anomalies vs. Total Loss
Understanding severity
Anomalies (protanomaly, deuteranomaly, tritanomaly) involve defective cones with reduced sensitivity. Total losses (protanopia, deuteranopia, tritanopia) involve complete absence of cone type.
How the Simulation Works
Color vision depends on three types of photoreceptor cone cells, each sensitive to different wavelengths: L-cones (long wavelength/red), M-cones (medium wavelength/green), and S-cones (short wavelength/blue). Normal trichromatic vision combines signals from all three types to perceive millions of colors.
When one cone type is absent (dichromacy) or malfunctioning (anomalous trichromacy), the visual system receives incomplete color information. Our simulator replicates this by applying transformation matrices to each pixel's RGB values. These matrices are based on colorimetric research and empirically validated against real color blindness perception studies.
For deuteranopia (green blindness), the matrix redistributes green wavelength information to red and blue channels, simulating how the brain compensates when M-cones are missing. This causes reds, greens, and browns to converge toward similar hues. The mathematics involves linear algebra transformations in RGB color space, but the result is a pixel-perfect representation of colorblind perception.
Unlike simple color filters or opacity overlays, true color blindness simulation requires precise mathematical transformations. We use the Brettel, Viénot, and Mollon algorithms—the scientific standard for digital color vision deficiency simulation. This ensures accuracy sufficient for professional accessibility auditing.
How to Use This Tool
Enter Website URL (Automatic Capture)
Simply paste any website URL into the input field and click "Generate Preview." Our tool automatically captures a screenshot using a headless browser. Choose between Desktop (1920x1080) or Mobile (375x667) viewport to test different screen sizes. The screenshot is captured instantly—no manual work required.
Or Upload Your Own Screenshot
Prefer to use your own screenshot? Click "Select Screenshot" or drag and drop an image into the upload area. This is useful for testing designs still in development, localhost sites, or specific page states (modals, hover effects, etc.). Supports JPG, PNG, GIF, WebP up to 10MB. All processing happens in your browser—images are never uploaded to servers.
View Simulations
Once your screenshot loads, the tool instantly generates simulations for all 8 types of color blindness. Use the dropdown selector to switch between types and see a side-by-side comparison with the original. Scroll down to see thumbnail previews of all types at once. Focus on deuteranopia (most common, ~6% of males) and protanopia (second most common, ~1% of males) for maximum impact.
Analyze & Export Results
Look for UI elements that become unclear or invisible: buttons that lose visual distinction, text with insufficient contrast, color-coded charts that become meaningless, or navigation elements that blend together. Click "Download" to save simulations for documentation, presentations, or sharing with your team. Use these images to demonstrate accessibility issues to stakeholders and track improvements over time.
Pro Tip: Test Multiple Pages
Don't just test your homepage. Check your dashboard, forms, error states, checkout flow, and mobile navigation. Color accessibility issues often hide in complex interfaces and interactive elements that look fine on landing pages.
Common Accessibility Problems Found
Red/Green Status Indicators
Problem: Success (green) and error (red) states look identical to deuteranopic users.
Fix: Add icons (✓ for success, ✗ for error), use blue/orange instead of green/red, or add text labels.
Insufficient Contrast
Problem: Text becomes unreadable when colors that seem distinct to normal vision appear similar to colorblind users.
Fix: Maintain 4.5:1 contrast ratio minimum. Use contrast checkers alongside color blindness testing.
Color-Coded Charts
Problem: Data visualization relying only on color to distinguish categories or values.
Fix: Add patterns, textures, direct labels, or use colorblind-friendly palettes (ColorBrewer, Tableau).
Links Without Underlines
Problem: Links identified only by color become invisible in body text.
Fix: Underline links, use bold weight, add icons, or ensure sufficient contrast even without color distinction.
Accessibility Best Practices
Never rely solely on color. The fundamental principle of color accessibility is redundancy. Every piece of information conveyed through color must also be available through another visual means: shape, position, pattern, text, or iconography. If removing all color from your interface breaks functionality, you have an accessibility problem.
Follow WCAG 2.1 guidelines. Level AA requires 4.5:1 contrast for normal text and 3:1 for large text (18pt+ or 14pt+ bold). Level AAA requires 7:1 and 4.5:1 respectively. These ratios ensure readability even when color perception is impaired. Use tools like WebAIM's Contrast Checker in combination with color blindness simulation.
Choose colorblind-friendly palettes. When possible, use palette systems designed for accessibility. Avoid red-green combinations (use blue-orange instead). Tools like ColorBrewer and Viz Palette offer scientifically-designed color schemes that remain distinguishable across all color vision types.
Test early and often. Integrate color blindness testing into your design workflow, not as an afterthought before launch. Test wireframes, prototypes, and every significant UI change. Include colorblind individuals in user testing when possible—simulations are accurate but nothing replaces real user feedback.
Document your accessibility decisions. Keep records of color choices, contrast ratios, and testing results. Export simulations from this tool for design documentation. This evidence demonstrates compliance and helps maintain accessibility standards as your team grows and evolves.
Your Privacy is Protected
All image processing happens locally in your browser using JavaScript. Your website screenshots are never uploaded to our servers or stored anywhere. The color blindness simulation runs entirely on your device, ensuring your designs and data remain completely private and secure.