Accessibility / Colour

Colour Blindness Simulator

See a picture, chart, or design as people with protanopia, deuteranopia, tritanopia, or achromatopsia see it, side by side, with milder forms too.

Colour Blindness Simulator: Each kind of colour blindness is the loss of one of the three cone types in the eye. The simulator converts every pixel to cone responses and projects it onto the colours a person without that cone type can tell apart, using the method of Brettel, Viénot and Mollon (1997), the reference in the research literature, as the open-source DaltonLens project implements it. Milder forms blend the result with the original. Achromatopsia keeps only brightness. Runs 100% locally in your browser with zero server file uploads.

Category
Everyday tools
Runs
In your browser
Cost
Free · no sign-up
Availability
Ready to use
Colour blindness simulatorLocal processing

Runs entirely in your browser

Choose or drop a picture, screenshot, or design

Click, drag and drop, or paste · stays on this device

At 100%, a cone type is missing entirely (dichromacy).

Normal vision The picture as it is
Deuteranopia No green cones: reds and greens look alike; the most common, about 6% of men with its milder form
Protanopia No red cones: reds look dark and alike with greens; about 2% of men with its milder form
Tritanopia No blue cones: blues and greens, and yellows and pinks, look alike; rare
Achromatopsia No colour at all, only light and dark; very rare

Red–green and blue–yellow

Protan and deutan colour blindness both merge reds, oranges, yellows, and greens into a range of yellowish browns; protans also see red as darker. Tritans confuse blue with green and yellow with pink. In all forms, differences in lightness remain visible, which is why contrast matters more than hue.

To check that text stands out from its background by lightness, use the colour contrast checker.

Charts and maps

Charts suffer most, because their legends match lines and bars by colour alone. Label lines directly, vary lightness as well as hue, or use a palette made for colour vision deficiency, such as blue with orange. To pull the colours out of an existing chart and compare them, use the colour palette extractor.

How to use it

  1. Choose or drop a picture, screenshot, or design; a sample of colours is shown until you do.
  2. Compare the five versions side by side; lower the strength for the milder forms.
  3. Download any simulated version to share it with your team.

Privacy & limitations

Your picture is processed in your browser and never uploaded.

Related tools

Contrast CheckerPalette ExtractorColor Converter

Frequently asked questions

How common is colour blindness?

About 8% of men and 0.5% of women of Northern European descent have some red–green colour blindness, most often a mild deuteranomaly. Blue–yellow (tritan) colour blindness and total colour blindness are rare.

How do I make a design work for colour-blind people?

Do not rely on colour alone: add labels, patterns, or icons, and keep strong contrast in lightness. Red and green side by side is the pairing most often confused; blue and orange is a safer pair.

Is the simulation exact?

It is a good model of how dichromats match colours, not of what each person experiences, which varies. Use it to find colours that become hard to tell apart.

Free tool · runs in your browser · no account required