About ColorVision

Why this site exists

Around 300 million people have some form of colour vision deficiency, and a large share of them have never been screened. The reason is mundane: screening has historically required being in a room with a clinician and a printed plate book. For most people that only happens if something else prompts an eye examination first.

The consequence is that colour vision deficiency tends to be discovered late, and often by accident — a failed occupational check in someone’s twenties, or a school-age child who was quietly struggling with colour-coded materials for years. Neither is dangerous, but both are avoidable.

This site makes a reasonable first check freely available to anyone with a browser, and places it next to enough explanation that a result is actually usable. Free, no account, nothing behind a paywall.

What we build, and what we do not claim

The activities here are original implementations of published perceptual principles — pseudoisochromatic dot fields, hue arrangement tasks, and physiologically-based colour vision simulation. They are not reproductions of the clinical instruments they are inspired by.

That distinction is deliberate and we hold to it throughout. A clinical plate book is a specific published instrument, printed to controlled tolerances and read under standardised illumination. Our activities run on whatever display you happen to have, in whatever light you happen to be sitting in. Presenting our output as equivalent to a clinical result would be false regardless of how carefully we built the activity.

So we describe these as educational screens, we state their limits on every page, and we say plainly that they cannot be used for medical, licensing, employment or legal decisions. Our test methodology documents how each was constructed, and tool capabilities sets out what each one can and cannot measure.

How the content is prepared

Educational content is written and maintained by the ColorVision Editorial Team. Our editorial and medical content policy sets out the standards in full; in summary:

• Factual claims are grounded in primary research, government health information such as the National Eye Institute and MedlinePlus, or established clinical references.
• Where a page relies on a specific source, that source is linked directly so readers can check the evidence rather than take our word for it.
• Pages carry a last-updated date, and are revised when material information changes.
• We correct substantiated errors. If you find one, our contact page is the fastest route.

We are explicit about the boundary between education and medicine. Nothing here is a diagnosis or individual medical advice. A new or worsening change in colour vision, a change affecting one eye, or any accompanying visual symptom should be assessed by an optometrist or ophthalmologist — and that advice appears on the tools themselves, not only in a disclaimer.

Privacy, and why it is architectural

Every activity runs entirely in your browser. Test responses, results, and any image you load into the simulator are processed on your device and never transmitted to us. We do not ask for an account, and we cannot associate a result with a person because we never receive one.

This is not a policy choice that could be quietly reversed; it is how the tools are built. The privacy policy covers the remaining details, including the anonymous aggregate analytics we use to understand which pages are read.

Independence

The site is supported by advertising. No manufacturer of colour vision tests, corrective lenses or eyewear funds this site, influences its content, or has been paid to appear in it. When we describe the limits of a method — including our own — that assessment is not constrained by anyone’s commercial interest.