Monitor test

Check your screen for dead pixels

Seven full-screen colours make dead pixels, stuck pixels, backlight bleed and banding easy to spot. Click through them, then tell us what you saw.

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Before you start

  • Wipe the screen. Dust looks a lot like a dead pixel.
  • Dim the room for the black screen, so backlight bleed shows up.
  • Click, or press → or Space, for the next colour. Right-click or ← goes back, and Esc finishes.
–Resolution
–Refresh rate
–Display scaling
–HDR on
–Colour range

Start the full-screen test and look closely at each colour.

Spotted something? Try these first

  • Clean the screen with a dry microfibre cloth and look again. A speck that moves when you wipe was dust.
  • A stuck pixel (one colour, not black) sometimes recovers if you gently rub the spot through a soft cloth while the screen is on, or leave a video of rapidly changing colours playing over it for 20 minutes.
  • For banding, check your graphics card is sending 8-bit or 10-bit colour and full RGB range, and turn off any "dynamic contrast" setting on the monitor.
  • For a refresh rate lower than advertised, pick the higher rate in your display settings and use a DisplayPort or HDMI 2.1 cable that supports it.
  • New screen? Most UK retailers accept returns within 14 days, and makers publish a "pixel policy" saying how many dead pixels count as faulty.

Shopping for a new monitor?

Working fine

Looks faulty?

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If you're upgrading anyway, our sister site Sudo Picks compares monitors on panel type, refresh rate, size and price.

Dead pixels don't recover, and bleed rarely improves. Our sister site Sudo Picks compares monitors on panel type, refresh rate, size and price.

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How to use the monitor test

Press Start the full-screen test. The screen fills with black, white, red, green, blue, grey and finally a smooth fade. Take your time on each one and look across the whole screen, including the edges. A short hint says what to look for, then fades away so it isn't in the way.

When you finish, pick the answer that matches what you saw and the test tells you what it means.

Dead pixels and stuck pixels

A dead pixel gets no power, so it stays black on every colour and is easiest to see on white. A stuck pixel has one of its red, green or blue parts stuck on, so it shows as a bright coloured dot, easiest to see on black. Stuck pixels sometimes recover; dead ones don't.

Backlight bleed

LCD screens are lit from behind, and some light can leak around the edges. On a black screen in a dark room it shows as cloudy glow near the corners. A little is normal, especially on IPS panels, which also show a silvery "IPS glow" that changes as you move your head. OLED screens don't have a backlight, so they don't bleed.

Refresh rate

The refresh rate is how many times a second the screen updates. Office screens run at 60 Hz, and gaming monitors at 144 Hz or more. The reading comes from how often your browser draws the page. If it's lower than your monitor's rating, the screen is probably set to a lower rate in your display settings, or the cable can't carry the higher one. Laptops on battery saver often drop to 60 Hz too.

Common questions

How many dead pixels is acceptable?

It depends on the maker. Many follow the ISO 9241-307 class 1 standard and will only replace a screen with a few dead pixels, but several premium brands replace a monitor for a single bright pixel. Check the pixel policy on the maker's website. Within 14 days of buying online, UK consumer law lets you return it anyway.

Can a dead pixel be fixed?

A truly dead pixel, one that's black on every colour, can't be fixed at home. A stuck pixel, one showing a single colour, sometimes recovers with gentle pressure through a cloth or a flashing-colour video left over it.

Why does the refresh rate say 60 Hz on my 144 Hz monitor?

Windows and macOS often default to 60 Hz. Open your display settings and pick the higher rate. If it isn't offered, the cable or port may not support it: use DisplayPort, or HDMI 2.0 or newer.

Does this work on a phone or laptop screen?

Yes. On iPhones the browser bars stay visible, so scroll down slightly or turn the phone sideways to fill more of the screen.