How to use it
- Press Start colour check. The screen fills with black, the first colour.
- Click, tap or press the right arrow or Space to move through white, red, green, blue and 50% grey.
- Look for a dot that does not change with the colour: a dot that stays black is dead, and a dot that stays one colour is stuck.
- Press Esc to close the check. Use Start pixel fixer only if you have read its warning.
What to look for
A dead pixel stays black on every colour, because it no longer lights up. A stuck pixel stays lit in one colour while the rest of the screen changes. Both show best on a solid colour, so look at each one closely, including the edges and corners, and from a normal distance and a slight angle.
Black shows bright dots, white shows dark ones and red, green, blue and grey show the stuck colours best.
How the check works
Start the check and the screen fills with one solid colour. Step to the next one with a click or tap, the right arrow or Space; the left arrow goes back. Esc, or the browser's own control for leaving full screen, closes the check. Nothing is recorded: the colours are drawn on your screen and the page keeps no record.
The pixel fixer
A stuck pixel can sometimes be relaxed by flashing it. The fixer changes the colour of a small block about every 0.4 seconds, which is at most 2.5 flashes a second, and moves the block across its box. Flashing light can trigger seizures in people with photosensitive epilepsy, so read the warning first and stop the fixer at once if you feel unwell. The fixer does not repair dead pixels, which are damaged hardware.
Example: two defects on one screen
One dot stays black on all six colours, so it is a dead pixel. A second dot is bright green on black, white, red, blue and grey, so it is a stuck green pixel. Write down where each one is, then read the defect rules in your warranty before you contact the maker.
Frequently asked questions
Will this test fix a dead pixel?
No. A dead pixel is damaged hardware that no software can repair. The pixel fixer can sometimes relax a stuck pixel, but it does not repair the screen.
Is the pixel fixer safe to use?
Not for everyone. It flashes colours, so it can trigger seizures in people with photosensitive epilepsy. It stays off until you tick the box and start it, and you should stop it at once if you feel dizzy, uncomfortable or unwell.
Why does the colour check fill the whole screen?
A solid colour across the full screen shows defects that a small window could hide behind a border or a page element. Full screen also removes the page content and the browser's controls from view.
Does the check work on a phone or tablet?
Yes. Tap to change colours. On some phones full screen is limited, and then the colour fills the browser window instead, which still shows defects clearly.
What does the 50% grey show?
Mid grey shows uneven brightness, dark patches and bright patches that a solid black or white screen can make harder to see.
Sources
- WCAG 2.1 Understanding: Three Flashes or Below Threshold, W3C
- Fullscreen API, WHATWG living standard
- Fullscreen API, MDN Web Docs
Figures and text last checked on Tuesday, November 10, 2026.