Dead pixel test
Open a full-screen colour and look for dots that do not change with it.
In full screen: click, Space or → for the next colour, ← for the previous one, Esc to leave.
This browser cannot show an element full screen (iPhone). Add the page to the Home Screen and open it from there, in landscape, for an edge-to-edge view.
Stuck pixel exerciser (optional, flashing)
Photosensitivity warning. This tool flashes a small square in rapidly changing colours. Flashing light can trigger seizures in people with photosensitive epilepsy. Do not use it if you or anyone who can see the screen has epilepsy or has had a seizure; stop at once if you feel unwell.
It can sometimes free a stuck (coloured) pixel; it cannot repair a dead (black) one. Click to place the grey square over the pixel, then press Enter or click the square to start. Any click, any key or Esc stops it immediately; it also stops by itself after 10 minutes.
Click where the stuck pixel is. Nothing flashes yet. Esc closes.
Result
Waiting for input
Loading the instrument…
A dead pixel stays black on every colour; a stuck pixel stays red, green or blue. This test fills the whole screen with one solid colour at a time. Clean the screen, open each colour full screen and look for dots that do not change. The browser cannot see pixels, so the check is visual.
How to read the readings
| Colour | What shows up |
|---|---|
| Black | stuck or hot pixels (bright dots) |
| White | dead pixels (dark dots) and dust |
| Red, green, blue | stuck sub-pixels of the other colours |
| Grey 50 % | clouding and uneven backlight |
What a browser cannot measure
- The check is by eye; the page cannot read what the panel shows.
- iPhone has no element full screen: add the page to the Home Screen for an edge-to-edge view.
- The optional stuck pixel exerciser is off by default. It flashes only a small square, never the full screen, and starts only after a photosensitivity warning and confirmation. It helps some stuck pixels and never dead ones; there is no guarantee.
Fixing the fault
Windows
- For a stuck (coloured) pixel, run the optional exerciser over it for 10–20 minutes; if it stays, it is a hardware fault.
- Note the position of each pixel and the panel’s warranty pixel policy.
macOS
- Note the position of each pixel and contact the seller within the return period.
Linux
- Same as other systems: document position and colour of each pixel.
Questions
What is the difference between dead and stuck pixels?
A dead pixel stays dark on every colour. A stuck pixel stays lit in one colour. Both show best on full-screen solid fields.
Can a stuck pixel be fixed with flashing colours?
Sometimes. The optional exerciser on this page flashes a small square over the pixel; it can free a stuck sub-pixel but never revives a dead one. It is off by default because flashing can trigger seizures, and it starts only after you confirm the warning. A warranty claim is the reliable route.
Method and algorithm version
Algorithm version 1 (2026-10). Solid fills only, switched by the user; the cursor hides after one second. The exerciser cycles red, green, blue, white and black once per frame inside a square of 16, 32 or 64 CSS px, well under the WCAG 2.3.1 small-area limit; any click, key or Esc stops it, and it stops by itself after 10 minutes or when the tab is hidden.