How the color blind test works
Each plate is a circle of dots in different sizes and shades. Some dots form a number. The number and the background differ in hue along a line of colours that people with a colour vision deficiency confuse, while the brightness of the dots is mixed at random, so the number can't be found by lightness alone. If you see the hue difference, the number stands out; if you don't, the plate looks like random dots.
- Control plate: visible to almost everyone. If you miss it, check the screen before reading anything into the rest.
- Seven red-green plates, from strong to subtle colours. These detect the common protan (red) and deutan (green) deficiencies.
- Three blue-yellow plates for the rare tritan type.
Ishihara color blind test: what it is
The Ishihara color blind test was published in 1917 by the Japanese ophthalmologist Shinobu Ishihara and is still the most widely used screening test for red-green colour blindness. It is a printed book of plates viewed in daylight. The plates on this page follow the same principle but are drawn by your browser from random dots each time; they are not copies of the original plates, and a screen can't reproduce their exact colours. Eye doctors use the printed version, or an anomaloscope, for a diagnosis.
What your result means
| Result | What it suggests |
|---|---|
| All or nearly all plates read | Typical colour vision on this screen |
| Missed only the faintest red-green plates | Could be the screen or a mild red-green deficiency (anomaly) |
| Missed most red-green plates | Pattern typical of protan or deutan colour blindness |
| Missed most blue-yellow plates | Rare tritan deficiency, or a yellowish screen setting such as night mode |
| Missed the control plate | Screen problem: brightness, filter or forced dark mode |
About 1 in 12 men and 1 in 200 women have some form of colour vision deficiency, almost always red-green, because the genes for the red and green cones sit on the X chromosome. Blue-yellow deficiency is much rarer and affects men and women equally.
Reverse color blind test
The reverse color blind test turns the idea around. In these hidden-number plates, the number differs from the background mainly in lightness, while strong red and green noise covers it. People with typical colour vision are distracted by the red and green and often can't find the number; some people with red-green colour blindness are less affected by that noise and see it more easily. The effect is real in printed hidden-digit plates but weak and variable on screens, so treat this mode as a curiosity rather than a result.
Color blind test pictures and screens
Color blind test pictures on a screen depend on the screen. Phone night modes, "eye comfort" filters, wide-gamut monitors without colour management and very low brightness all shift the colours of the plates. For the fairest online color blind test, use a phone or monitor in its standard colour mode, take the test indoors in normal light, and repeat it on a second device if a result surprises you.
How we tested this tool
We drew plates with fixed seeds (about 900 dots each) and checked that no dots overlap, that every dot is drawn in the colour assigned to it, and that dots inside the number get figure colours. In the red-green and blue-yellow plates the average luminance of the number and the background differs by 0.2% or less, so brightness doesn't give the number away. This check found a real problem in our first version, where the orange numbers were up to 48% darker than the green background; we fixed it by matching luminance dot by dot. We then simulated colour blindness with the Machado, Oliveira and Fernandes (2009) model: for deuteranopia the colour difference (ΔE) between number and background drops from 71, 52 and 37 on the easy, middle and hard red-green plates to 4, 8 and 9, and for protanopia to about 19 to 23, while the control and blue-yellow plates stay clearly visible. We checked scoring, the "I see no number" button, the result texts and repeating the test, on a desktop browser and at a 375 px phone width. We have not validated the plates against a clinical test with real participants; that is exactly why this is not a diagnostic test.
Frequently asked questions
Is this an Ishihara color blind test?
It works the same way: numbers made of coloured dots hidden in other dots. The plates are our own and are generated new each time, not copies of the original Ishihara plates, and a screen can't match printed plates under proper light, so it is a screening exercise, not a diagnosis.
Can an online color blind test be accurate?
It can point to a likely red-green or blue-yellow deficiency, but screens differ in colour, brightness and settings such as night mode. Only an eye doctor's test with calibrated plates or an anomaloscope can diagnose colour blindness.
What is a reverse color blind test?
It uses hidden-number plates where the number differs from the background mainly in lightness while red and green noise hides it. People with typical colour vision often struggle to see it; some people with red-green colour blindness see it more easily.
How common is color blindness?
About 1 in 12 men and 1 in 200 women have some form of colour vision deficiency, almost always red-green. Blue-yellow deficiency is rare.
Why did I miss the control plate?
Almost everyone can read the control plate, so missing it usually means the screen is too dim, a blue-light or night mode filter is on, or the browser is forcing dark mode. Fix that and take the test again.
Can kids take this color blind test?
Yes, if they can read numbers; an adult can type the answer they say. For young children who don't know numbers yet, eye doctors use special picture or path plates.