Color Blind Accessibility Grader: Grade Contrast for Protanopia, Deuteranopia & Tritanopia, Free & Online

Use this free color blind accessibility grader in your browser. No sign-up, no download and no upload: everything runs on your own device, so your data stays private.

What this tool does

A colour pair can pass a normal contrast check and still fail for a colour-blind reader, because the two colours may collapse to similar tones under protanopia, deuteranopia or tritanopia simulation. This tool computes the WCAG contrast ratio and shows simulated swatches for all three types, so you grade the pair for real readers, not just for the formula.

How to use it

Paste or type your foreground and background colours in the box above.
Adjust any settings, such as cutoffs, scales or styles, to match your data.
Click the run button and read the output below the tool.
Check the summary numbers before you copy anything into a document.
Copy the output, code or image into your figure, slide or report.

Worked example

Test dark teal #0f766e on white. The ratio is about 5.7:1, a solid AA pass, and the simulated swatches stay clearly darker than the background under all three simulations. Try a light red on light green next and watch the simulations wash out even when the raw ratio looks acceptable.

Tips for better results

Never use colour alone to carry meaning; pair it with a label, shape or pattern.

Honest limits

Simulations are approximations of colour vision, not a diagnosis of any individual reader, and the tool grades one pair at a time. For a full palette, test every pair you actually use.

Choosing the right settings

Start with the default values. They are chosen to show a sensible result at once, so you can see the layout before you touch your own data. Then change one setting at a time. Changing one thing at a time is the fastest way to learn what each control does, and it stops two changes from cancelling each other out. If the output looks wrong, check the input format first: a missing comma, a swapped column or a stray space causes most errors, and the tool reports what it received in its summary line.

Using the result in a figure

For a figure, keep the output simple. One message per figure, short labels, and a caption that states the method and the settings you used will serve readers better than a dense, decorated chart. If a journal or supervisor will see the result, note the tool name, the input values and any cutoff in your methods or caption, so the figure can be reproduced later. That habit also helps you: six months from now, the caption is the only record of how the figure was made.

Common questions

Do I need an account? No. The color blind accessibility grader runs entirely in your browser with no sign-up and no saved data.

Is my data uploaded anywhere? No. Your foreground and background colours stays on your device, which is why the tool is safe for unpublished work.

Can I use the output in a paper or presentation? Yes. The output is yours to reuse; just check it visually once, note the settings in your caption, and credit the method, not the tool, in your references.

What if the result looks wrong? Check the input format first, then change one setting at a time. Most errors come from a missing comma, a swapped column, or a value outside the expected range, and the summary line under the tool shows what it actually received.

Try the color blind accessibility grader above with the sample data, then with your own. It is free, it needs no account, and it works in any modern browser.

When you reuse the result, keep a short record of the inputs and settings you used. A one-line note in your project file, such as the data pasted, the cutoff chosen and the date, is enough to reproduce the figure later. If a collaborator questions a number, that note lets you rebuild the exact output in seconds instead of guessing what changed.

Embed this tool on your website — free

Copy the code below to add this working tool to your own page. A small credit link stays with it — that’s all we ask.