10 min
How to Check a New Monitor Before the Return Window Closes
Dead pixels, backlight bleed and IPS glow are three different things with three different verdicts. Here is what to check, and what counts as a defect.
How Many Dead Pixels Are Acceptable on a Monitor
You unpack a new monitor, run a test, and find a single pixel stuck on bright green. Can you send it back? Very often the honest answer is: it depends on the return window, not the warranty, because the standard most panels are sold under allows more faulty pixels than most buyers would guess.
8 min read · updated 21 September 2026 · links to 6 tools
In short
Most monitors are sold to ISO pixel fault class II, a standard that sets a maximum number of faulty pixels per million. Class II allows 2 always-on (bright) pixels, 2 always-off (dark) pixels and 5 faulty sub-pixels in every million pixels, with no clusters of bright or dark faults. Because the allowance is per million, it grows with resolution: a 1920 × 1080 monitor has about 2.1 million pixels, so it may have about 4 bright and 4 dark pixels, while a 3840 × 2160 4K monitor has about 8.3 million and may have about 16 of each, plus about 41 faulty sub-pixels, and still be within the standard. Manufacturers' own policies can be stricter: some premium lines are replaced for a single bright pixel. So check a new monitor on the first day, while an ordinary return is still possible, then compare anything you find with the maker's published pixel policy for that model.
Three kinds of faulty pixel
Every pixel on an ordinary LCD is made of three sub-pixels, red, green and blue. The pixel fault standard sorts faults into three types, and the type matters because the allowances are different.
| Type | What you see | Common name |
|---|---|---|
| Type 1 | A pixel always lit, usually white, visible on a black screen | Bright or hot pixel |
| Type 2 | A pixel always off, black on a white screen | Dead pixel |
| Type 3 | One sub-pixel stuck on or off, showing as a red, green or blue dot | Stuck pixel |
A stuck sub-pixel can sometimes be coaxed back by flashing colours over it for a while; a truly dead pixel cannot. It is worth trying before you decide it is permanent, but it does not always work.
The standard: pixel fault classes
The classes come from ISO 13406-2, published in 2001, which was withdrawn and replaced in 2008 by parts of ISO 9241, including ISO 9241-307, with the same class scheme. Each class sets a maximum number of each fault type per million pixels, and a separate limit on clusters, where several faults sit close together.
| Class | Type 1 (bright) | Type 2 (dark) | Type 3 (sub-pixel) | Clusters of type 1 or 2 | Clusters of type 3 |
|---|---|---|---|---|---|
| I | 0 | 0 | 0 | 0 | 0 |
| II | 2 | 2 | 5 | 0 | 2 |
| III | 5 | 15 | 50 | 0 | 5 |
| IV | 50 | 150 | 500 | 5 | 50 |
All figures are the most allowed per million pixels. Class I, zero faults of any kind, is the strictest; class II is the level most consumer panels are sold at.
What class II allows on your screen
Because the allowance is per million pixels, the same class permits more faults on a higher-resolution screen. The table applies the class II limits to common resolutions. The standard itself does not say how to round a fractional result, so the figures are shown to one decimal place.
| Resolution | Pixels | Bright (type 1) | Dark (type 2) | Sub-pixel (type 3) |
|---|---|---|---|---|
| 1920 × 1080 | 2,073,600 | 4.1 | 4.1 | 10.4 |
| 2560 × 1440 | 3,686,400 | 7.4 | 7.4 | 18.4 |
| 3440 × 1440 | 4,953,600 | 9.9 | 9.9 | 24.8 |
| 3840 × 2160 | 8,294,400 | 16.6 | 16.6 | 41.5 |
What manufacturers actually promise
The standard is a floor, not a promise, and each manufacturer publishes its own pixel policy, often different for different product lines. Dell is a clear example: its ordinary monitors follow industry norms, while models covered by its Premium Panel Exchange are replaced during the warranty for even one bright pixel or bright sub-pixel.
Look up the policy for your exact model before you rely on a warranty claim. Search the manufacturer's support site for the model number and “pixel policy”, and note whether it counts bright and dark faults differently.
The return window beats the warranty
A warranty claim is judged against the manufacturer's pixel policy, which is often close to class II. A return to the shop within its normal return period usually is not: you can often send back a monitor you are unhappy with for any reason. So a single bright pixel that no warranty would cover can still be a perfectly good reason for a return in the first days.
That makes the first day the most important time to test. Check every new monitor as soon as it is set up, and keep the box until you have.
How to check a new monitor for faulty pixels
- Clean the screen gently first; dust looks exactly like a dark pixel.
- Open the dead pixel test in full screen and step through white, black, red, green and blue.
- On black, look for lit dots (type 1). On white, look for black dots (type 2). On red, green and blue, look for a dot in the wrong colour (type 3).
- Photograph anything you find with the test colour behind it, and note its position.
- For a coloured dot, try the stuck pixel fixer for a while, then test again.
- Compare what remains with your return period first, and the manufacturer's pixel policy second.
Frequently asked questions
How many dead pixels are acceptable on a monitor?
Under ISO pixel fault class II, the level most monitors are sold at, up to 2 bright, 2 dark and 5 sub-pixel faults per million pixels. That is about 4 bright pixels on a 1080p screen and about 16 on a 4K screen. A manufacturer's own policy may be stricter.
Can I return a monitor for one dead pixel?
Usually not under the warranty, because one fault is within most pixel policies. But within the shop's normal return period you can often return a monitor for any reason, so test it on the first day.
What is ISO 9241-307 class II?
The pixel fault class most consumer monitors are sold to. It allows at most 2 always-on, 2 always-off and 5 faulty sub-pixels per million pixels, with no clusters of bright or dark faults. It replaced ISO 13406-2 in 2008 with the same class scheme.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel is always off and shows as black. A stuck pixel has a sub-pixel stuck on or off and shows as a red, green or blue dot. Stuck pixels can sometimes be fixed by flashing colours; dead pixels cannot.
Why does a 4K monitor allow more dead pixels?
Because the pixel fault standard counts faults per million pixels. A 4K screen has about 8.3 million pixels, four times a 1080p screen, so the same class allows four times as many faults.
Do all manufacturers follow the same dead pixel policy?
No. Each publishes its own, sometimes different for different product lines. Dell, for example, replaces monitors covered by its Premium Panel Exchange for a single bright pixel during the warranty.
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