# How to check a monitor or laptop screen before the return window closes

Source: https://spolvero.design/articles/check-screen-before-return-window/
Updated: 2026-10-01
Tool: https://spolvero.design/tools/device-tests/dead-pixel-test/

> Check the screen the day it arrives. Clean it, set brightness to maximum, open a fullscreen colour test and look across solid black, white, red, green, blue and grey. A dot that is black on every colour is a dead pixel, a white one is a hot pixel, and a coloured one is stuck. Then view black in a dark room for backlight bleed. Mark and photograph every fault before you contact the seller.

A screen fault is cheapest to deal with on the first day. Inside the return window a retailer will usually take a screen back without an argument. After it, you are relying on the maker's warranty, and that often allows a few faulty pixels before a panel counts as defective. In the EU the legal minimum for an online purchase is 14 days, and many shops give no more than that, so the check should not wait for a free weekend.

This is the whole check. It takes about ten minutes.

## Before you start

1. **Clean the screen.** Use a dry microfibre cloth. Most "stuck pixels" are dust.
2. **Let it warm up** for a few minutes, and set brightness to maximum.
3. **Turn off anything that changes colour:** night mode, auto-brightness, and any eye-comfort setting.
4. **Use the native resolution.** Scaling blends a faulty pixel into its neighbours and can hide it.

## Step through six colours

Open the [dead pixel test](/tools/device-tests/dead-pixel-test/) and press **Go fullscreen**. Tap, click or press a key to move through black, white, red, green, blue and grey. On each one, look across the whole screen from about arm's length, corners and edges included.

| What you see | What it is | Best colour to spot it |
| --- | --- | --- |
| A black dot on every colour | Dead pixel | White |
| A white dot on every colour | Hot pixel | Black |
| A red, green or blue dot that vanishes on its own colour | Stuck pixel | Black, then the primaries |
| A soft speck that shifts as you move your head | Dust on the glass | White |
| A lighter patch at an edge, on black | Backlight bleed | Black, lights off |
| Cloudy or uneven areas | Poor uniformity | Grey |

When you find something, **press and hold on it** to put a numbered ring around it. With a mouse, right-click or Shift-click; from the keyboard, press M with the pointer over the spot. Marking the same place twice removes the ring. The ring is hollow, so the pixel stays visible inside it for a photograph.

## Check black in a dark room

Pixels are only half of it. Turn the room lights off, stay on the black field and look at the edges and corners.

- **Backlight bleed** is light leaking around the edge of the panel. It stays in the same place when you move your head.
- **IPS glow** is a pale sheen in the corners that shifts and fades as you change your viewing angle. It is a property of the panel type, not a fault.
- **Clouding** is uneven patches in the middle of the screen. The grey field shows it best.

A little bleed is normal on an LCD. Bleed you can see from your usual seat with a film playing is worth returning. OLED screens have no backlight, so on one of those, check grey for a colour tint and for faint ghosts of old images instead.

## What counts for a return

Inside the retailer's return window, you generally need no threshold at all: "it has a dead pixel" is enough. That is the reason to check now.

After that, the maker's warranty applies, and many makers work from the fault classes in ISO 9241-307, which took them over from the older ISO 13406-2. Most consumer screens are sold as Class II:

| Screen | Pixels | Always lit | Always dark | Sub-pixel faults |
| --- | --- | --- | --- | --- |
| 1920 × 1080 | 2.07 million | 4 | 4 | 10 |
| 2560 × 1440 | 3.69 million | 7 | 7 | 18 |
| 3840 × 2160 | 8.29 million | 16 | 16 | 41 |

Those are the numbers the standard permits, which is more than most people would accept. Some makers promise better, such as a replacement for a single bright pixel, so read the pixel policy for your exact model before you write to them.

## Record it

When you leave fullscreen, the test lists every mark by position, for example "top left, 12% across, 8% down", with an approximate pixel coordinate. **Copy result** puts that on the clipboard as plain text. Nothing is stored or sent; close the tab and it is gone.

Add a photograph of each fault on the colour that shows it best. Hold the phone square to the screen and tap to focus on the pixel. Then send both to the seller the same day. A dated message inside the window is what protects you if the reply is slow.

## If the pixel is stuck rather than dead

A stuck pixel sometimes frees itself. The test has a **Try to fix a stuck pixel** mode that flashes the colours four to five times a second and stops by itself after five minutes. It shows a flashing-light warning first: do not run it if anyone who can see the screen is sensitive to flashing light, and there is no need to watch it. It does nothing for a dead pixel, and it is not a reason to let a return window run out.

## Buying used

The same check works at a seller's table. Ask to open one web page, go fullscreen and step through the colours; it takes two minutes and installs nothing. While the laptop is open, the [keyboard test](/tools/device-tests/keyboard-test/) finds dead keys, and a [webcam check](/articles/webcam-test-before-interview/) covers the camera. The [laptop check](/tools/device-tests/laptop-check/) strings every test together, adds ports and battery health, and prints a record; [how to check a used laptop](/articles/how-to-check-a-used-laptop-before-buying/) explains each step. There are screen-specific notes for a [laptop](/tools/device-tests/dead-pixel-test/laptop/), a [phone](/tools/device-tests/dead-pixel-test/phone/) and a [TV](/tools/device-tests/dead-pixel-test/tv/).

## Questions

### How many dead pixels are acceptable on a new monitor?

Most consumer screens are sold as Class II under ISO 9241-307, which allows 2 always-lit, 2 always-dark and 5 sub-pixel faults per million pixels. On a 1920 × 1080 screen that works out at 4, 4 and 10. A maker's own warranty can be stricter, and a retailer's return policy usually asks for no reason at all inside the window.

### What is the difference between a dead, hot and stuck pixel?

A dead pixel is off: a black dot on every colour, clearest on white. A hot pixel is fully on: a white dot on every colour, clearest on black. A stuck pixel has one sub-pixel jammed on or off, so it shows as a red, green or blue dot and vanishes on a field of its own colour.

### Is backlight bleed a reason to return a screen?

It can be, but there is no pixel count to point to. Bleed is judged by eye, so the evidence is a photograph of a black screen in a dark room. Glow that shifts as you move your head is a normal property of IPS panels rather than a fault; bleed stays in the same place.

### Can a stuck pixel be fixed?

Sometimes. Flashing colours rapidly over a stuck pixel for a few minutes can free it. It never revives a dead pixel. Do not press on the screen, and if the screen is inside its return window, returning it is the surer fix.

### How do I check a used laptop screen before paying?

Open the colour test in the laptop's browser, go fullscreen at maximum brightness, and step through all six colours looking for dots, patches and lines. Tilt the lid to look for pressure marks on white and grey. It takes about two minutes and needs nothing installed.