How the test works
The page fills the screen with one solid colour. Red, green and blue are the built-in choices; the fourth tab takes any colour you type as a hex value or pick from the colour dialog. Before you start, the preview shows the colour in the island; on the full screen page the left and right arrow keys, or a tap, switch between the four. A small caption with the colour name, its hex value and a timer sits in the corner and fades out after a moment of stillness.
The three primaries each drive a single sub-pixel. On the red page only the red sub-pixels are lit, so a dark dot there means the red sub-pixel at that spot does not work, and a dot that only appears on green or only on blue points to the other two. A stuck sub-pixel shows the opposite way: a bright dot of one colour on the pages where that colour should be off.
- Check all three primaries. A defect that hides on red will show on green.
- Use full brightness. Blue in particular is dim, and small defects vanish at low brightness.
- Look from straight on and then move closer to anything that catches your eye.
Nothing is measured and nothing is sent. The page draws colours; that is all it does.
What the result means
The result card shows the last colour and how long it stayed up. What matters is what you saw:
- A clean field on all three primaries. All sub-pixels work. Combined with a clean white and black page, the panel has no pixel defects.
- A dark dot on one primary only. That sub-pixel is dead. It will also be visible as a slightly off-colour dot on white if you look closely.
- A bright dot of a colour on a page of another colour. A stuck sub-pixel. It is often fixable, see below.
- A colour that looks wrong compared with another device. Gamut, colour temperature or a colour profile, not a defect. Wide-gamut panels look more saturated on purpose.
- A colour that is uneven across the screen. A pink or green tint on one side is a uniformity issue and is easiest to see on white and mid grey.
What to do about a problem
Stuck sub-pixels respond, sometimes, to a fast alternating pattern over the spot for ten to twenty minutes. The dead pixel test page has the method. Dead sub-pixels do not respond to anything; they are the only real defect on this page, and the question is whether the count crosses the manufacturer's threshold.
Colour differences between screens are normal and rarely worth chasing. If two monitors on one desk look different, set both to the same colour temperature and the same picture mode, and give them half an hour to warm up before you compare again. If you need them to match for colour work, a colorimeter is the only reliable tool.
When to return or claim the warranty
A dead sub-pixel counts as a dark dot under the ISO 9241-307 classification most manufacturers use. Class I panels are replaced for any dot; Class II panels, which cover most consumer devices, tolerate a few per million pixels. Note which colour page showed the dot and where it is, take a close photo, and check the policy for your exact model. Do it inside the return window if you can: a return needs no argument, a warranty claim does.
Frequently asked questions
What is the custom colour for?
Anything the three primaries do not cover: matching a brand colour on two screens side by side, checking a colour you use in a design, a coloured light for a photo or a video call, or a specific shade a support agent asked you to display. Type a hex value such as #ff8800 or pick one from the colour dialog.
Why does red look orange, or green look yellowish?
Panels differ in gamut. A wide-gamut screen shows a deeper, purer red than an sRGB one, and a browser without colour management may render the same value differently on each. Compare the page on two devices rather than against what you expect; a colour that looks the same on both is a rendering choice, not a fault.
Can a solid colour repair a stuck pixel?
No. A static colour is for spotting defects, not fixing them. Freeing a stuck sub-pixel needs rapid switching between colours over the same spot for several minutes, and even that only works sometimes. Use the colour pages to confirm which sub-pixel is stuck before you try.
Why can I only see a dot on the blue page?
The eye is least sensitive to blue, so the blue page looks dim and small defects on it are easy to miss. A dot visible only on blue means the blue sub-pixel has failed. Check in a dim room with the screen at full brightness and look from closer than usual.
Does this page calibrate my screen?
No. It draws exact sRGB values, which is all a web page can do. Calibration adjusts the panel's output so those values appear correctly, and that takes a colorimeter and a profile. The page is useful to see the result of a calibration, not to make one.