About ColorBlindCheck
A free, private place to check your color vision and get a plain-words answer.
ColorBlindCheck.app lets you take a color blind test, an astigmatism check and a simple eye test in your browser, with explanations written in plain English. Nothing is sent to us or saved: the tests run on your device.
How we make the tests
- Our own plates. Every dot plate, number and shape is generated by our own code, with a new random pattern each time. We do not copy plates from the Ishihara test or any other published test.
- Colors chosen with a model. We chose plate colors with the Machado et al. (2009) model of color blind vision, so that the number cannot be read from brightness alone. The model is an approximation, and mild color vision deficiency can still pass.
- Real Snellen sizes. The eye chart letters follow the standard Snellen geometry, where the letter height subtends 5 arcminutes. Our block letters are drawn by us.
How we write
Every medical statement comes from a source we read, such as the National Eye Institute, MedlinePlus, the American Academy of Ophthalmology and the NHS. The sources are listed at the bottom of each page. We do not invent numbers. When sources do not say something, we leave it out.
What we are not
We are not a medical service. The tests are screening tools, not a diagnosis, and the pages have not been reviewed by an eye care professional. Read the medical disclaimer.
Contact
Questions, corrections or ideas: info@colorblindcheck.app.
Last updated: October 11, 2026