TenSecondCheck

Screen test

Full-screen colours make dead pixels easy to spot. Press Esc to leave full screen at any time.

Runs in your browser only

Full-screen colours

Tap or use the arrow keys to change colour. Esc leaves full screen.

Dead pixel or stuck pixel?

A dead pixel stays black on every colour, because it receives no power. A stuck pixel stays one bright colour — often red, green or blue — on every screen. Stuck pixels sometimes recover on their own; dead ones do not.

Gradient

A smooth gradient should fade evenly. Visible stripes or steps mean the screen is showing fewer shades than the image contains.

Refresh rate

Refresh rate — Hz

Approximate — measured over one second, and browsers may cap it when the laptop is saving power.

How to check a screen for dead pixels

Press Start full screen. The page fills with a single colour; tap the screen or use the arrow keys to move to the next one, and press Esc to leave. You can also click one of the swatches to open a particular colour directly.

Look across the whole screen on each colour, from a normal viewing distance and then a little closer. Wipe the screen first — a speck of dust on black looks exactly like a lit pixel.

Each colour is good at revealing something different:

  • Black shows pixels that stay lit, and light leaking around the edges.
  • White shows pixels that stay dark, stains and pressure marks.
  • Red, green and blue show a pixel where one colour part is stuck on or off.
  • Grey is the best test for uneven brightness: cloudy patches or darker corners.

The colour only changes when you tap or press a key, never on its own. This page never flashes.

Dead, stuck and hot pixels

A screen pixel is made of three tiny parts — red, green and blue — that mix into every colour.

  • A dead pixel gets no power. It stays black on every colour and is easiest to see on white.
  • A stuck pixel has one or two parts permanently on, so it glows red, green, blue or a mix of them on every background. It is most visible on black.
  • A hot pixel is stuck fully on and shows as a white dot on black.

The difference matters: a stuck pixel sometimes recovers; a dead one does not. If you find a mark, move the page slightly. A mark that stays in the same place on the glass is a pixel fault; one that moves with the image is in the picture you are viewing.

Gradient and banding

The gradient fades from black to white. On a good screen it looks smooth. If you see distinct steps or stripes, the screen is showing fewer shades than the image contains. Some banding in the darkest part is common on laptop screens. Heavy banding everywhere can also come from night-light filters, colour profiles or a low colour depth setting, so check those before blaming the panel.

Refresh rate

Press Measure and keep the window in view for a second. The result is roughly how many times per second the browser was able to redraw the page, which usually matches the screen’s refresh rate: 60 Hz on most office screens, and 90, 120, 144 Hz or more on gaming monitors, many phones and newer laptops.

A reading lower than you expect is rarely a fault. Common reasons are a display set to 60 Hz in the system settings, a laptop on battery power, or a power-saving mode. Measure again with the charger connected and nothing else running.

Touch test on phones and tablets

On a touch screen, a grid appears. Drag one finger slowly across every row. Each cell you pass fills in. A row or column that refuses to fill no matter how you approach it is a dead strip in the touch layer, a common result of a cracked or replaced screen.

Then place several fingers down at once and watch the counter. Most phones register several fingers together. If the counter changes while you are not touching anything, the screen is producing phantom touches, which usually means damage or moisture under the glass.

Common problems and what they mean

  • Faint shapes of old windows remain. That is image retention. On LCD screens it fades; on OLED it can become permanent burn-in if the same image stays on screen for very long periods.
  • Flicker at low brightness. Many screens dim by switching the backlight on and off very fast. Some people notice it as eye strain; raising the brightness usually makes it less noticeable.
  • Colours look wrong on one side. Check the viewing angle first. If it stays wrong when you look straight at it, the panel or its cable may be damaged.

When you have checked the screen, My device shows its resolution and pixel density as the browser reports them. Buying a used laptop or phone? The used device check includes the screen and touch tests and records the result, and the webcam test covers the camera above it.

If it does not work

On your system

  1. Restart the computer before deciding a pixel is dead — a stuck pixel sometimes clears on its own.
  2. Check the display cable at both ends if you see stripes, flicker or wrong colours on an external screen.
  3. Open Settings → System → Display → Advanced display to see the refresh rate the system is actually using.
  4. If the dark marks move when you change the image, they are content, not a screen fault.
  1. Open System Settings → Displays to check the resolution and refresh rate in use.
  2. Restart before judging a stuck pixel, and look at the spot on several different colours.
  3. For an external display, try another cable and another port before blaming the panel.
  1. Look at the same spot on black, white and each colour — a mark that stays on all of them is a pixel fault.
  2. Turn the brightness up to the maximum, because a dark room hides faint marks.
  3. Check display settings for a refresh rate option, which some phones lower to save battery.
  1. Turn the brightness up and turn off True Tone and Night Shift in Settings → Display & Brightness, because both tint the whole screen.
  2. Look at the same spot on several colours before deciding a pixel is faulty.
  3. A pressure mark that spreads when you push the screen is a damaged panel, not a stuck pixel.

Questions and answers

Can a stuck pixel be fixed?
Sometimes it recovers on its own after a restart or a few days of normal use. You will find tools online that flash rapidly changing colours over the pixel. We deliberately do not offer one: fast flashing can trigger seizures in people with photosensitive epilepsy. A dead pixel, which stays black, does not recover.
How many dead pixels are acceptable?
There is no single answer. Manufacturers publish their own pixel policies, and they differ by brand and by product line, sometimes depending on where on the screen the fault is. Check the warranty terms for your exact model before you buy or return a screen.
My screen is 120 Hz but the test shows 60. Why?
The system may be running the screen at 60 Hz — check the display settings. Laptops and phones also lower the refresh rate to save battery, and some browsers limit animation speed in the same situation. Plug the charger in and measure again.
Is the touch test accurate?
It shows every place where the screen reported a touch and how many fingers it saw at once, which is what you need to find dead strips and phantom touches. It cannot measure pressure or tell you how precise the touch position is to the millimetre.
Why does black look grey or glow at the edges?
Screens that use a backlight let some light through even when showing black. Brighter patches along the edges are called backlight bleed; a glow that shifts as you move your head is typical of IPS panels. Both are common, and whether they are acceptable is a judgement call. OLED screens show true black and do not have either effect.