color blindness simulator
See how a chart, screenshot or design looks to people with red-green or blue-yellow colour blindness — and check it before you publish.
or click to browse — JPG, PNG, WebP
Original / simulated
Drag across the picture to compare the original with the simulation.
Machado 2009 model
Around one man in twelve and one woman in two hundred sees colour differently. For most of them red and green are the problem: a chart line that is obviously red to you merges into the green one next to it, an error shown only in red looks like any other text, and a map legend stops matching the map. This simulator shows an image the way it appears to people with the main types of colour vision deficiency, so you can check a chart, an app screen, a slide or a poster before it goes out.
It uses the physiologically based model published by Machado, Oliveira and Fernandes in 2009. Because most colour-blind people are not completely colour-blind, you can also set the severity: 100% simulates the complete form, lower values the far more common milder forms. The calculation is done on linear light rather than on raw pixel values, the full-size image is processed in your browser, and nothing is uploaded.
three steps
Drop in a JPG, PNG or WebP — a chart, a screenshot, a design or a photo.
Start with green-weak at 100%, the most common problem, then try red-weak and blue-weak. Drag across the preview to compare with the original and look for colours that have merged.
If two things can no longer be told apart, make their colours differ in lightness, not just in hue, or add labels, patterns or icons. Download the simulated version to share with your team.
quick answers
Green-weak (deutan). It accounts for most colour vision deficiency, followed by red-weak (protan). If an image works for both, it works for the large majority of colour-blind viewers. Blue-weak (tritan) and total colour blindness are rare.
It follows a peer-reviewed model of how the cone cells in the eye respond, which makes it a reliable guide for design decisions. It cannot be exact for any one person: colour vision varies between individuals, and the result also depends on your screen.
Most colour-blind people have one weakened cone type rather than a missing one. 100% simulates the missing type (protanopia, deuteranopia, tritanopia); lower values simulate the milder anomalous forms, where colours are harder, but not impossible, to tell apart.
Do not rely on hue alone. Make the colours differ in lightness as well, label lines directly instead of using a legend, and add patterns or markers. Blue and orange stay distinguishable for all common types; red and green do not.
No. It shows what an image looks like; it does not correct colours. Use it to adjust your own design until it reads well in every simulation.
No. The image is opened and processed entirely in your browser, and the simulated version goes straight to your downloads.
