Screen Test

About the Screen Test

This free screen test fills your whole display with one flat colour at a time. On a perfect screen every pixel shows exactly that colour. Any dot that does not is a fault, and a flat colour is the only reliable way to see it — faults disappear into a normal desktop picture.

Use it on a new monitor, laptop, phone or TV before the return window closes, and on a second-hand screen before you pay for it.

It runs in your browser. Nothing is installed and nothing is sent anywhere.

What each test finds

• Black — the most important one. Any pixel that glows red, green, blue or white on black is stuck. Backlight bleed and IPS glow also show here, as pale clouds at the edges or corners.
• White — shows dead pixels as black dots, and reveals dust, smudges and scratches you normally never notice.
• Red, green and blue — each drives one colour channel on its own. A pixel with a failed sub-pixel shows as a dark dot on that colour but looks fine on the other two.
• Gradient — a smooth black-to-white ramp. Visible bands instead of a smooth fade means the panel struggles with tones, common on cheaper 6-bit displays.
• Grid — a fine one-pixel pattern, for checking sharpness and that your screen is running at its native resolution. If the grid looks blurry or uneven, the resolution or scaling is wrong.

Dead, stuck and hot pixels

The words get mixed up constantly, and the difference decides what you can do about it:

• A dead pixel gets no power. It is black on every colour, including white. It cannot be fixed.
• A stuck pixel is jammed on one colour. It stays red, green, blue or white even on black. These sometimes come back on their own, and sometimes recover after a pixel-fixer video or gentle pressure.
• A hot pixel is stuck fully white. Same idea as stuck.

The test to tell them apart is the black screen. Black background, bright dot = stuck. White background, black dot = dead.

Before you call it a fault

• Clean the screen first. Most "dead pixels" are dust or a fleck of dried liquid. Use a dry microfibre cloth.
• Look from straight on. IPS panels glow at the corners from an angle. That is normal and not a defect.
• Turn the room lights down for the black test, and let your eyes adjust for a few seconds.
• Check your screen is at native resolution. A scaled image makes everything look soft, and that is not the panel's fault.
• Know the manufacturer's policy before you claim. Most makers allow a small number of faulty pixels before a screen counts as defective, and the limit is often stricter for bright pixels on black than for dark ones.

Features

• Seven tests — black, white, red, green, blue, gradient and a fine grid
• Run all steps through the whole set in the order that finds the most
• True full screen, with nothing on top of the pixels you are inspecting
• The label fades away after a couple of seconds so it cannot hide a fault
• Keyboard and click control — space or click for the next, Esc to leave
• Works on monitors, laptops, phones, tablets and TVs with a browser

Good to know

• The on-screen label disappears on its own. Move the mouse or press a key to bring it back.
• On a TV, open the browser built into the set, or cast the tab. Picture modes that sharpen or smooth the image can hide faults — switch to a plain or game mode first.
• A phone with an OLED screen may show faint patches on grey. That is usually panel uniformity, not dead pixels.
• This is a viewing test. It cannot repair anything — it only shows you what is there.

How to use it

• Press Run all to step through every test, or pick a single colour
• On black, look for any dot that is not black — those are stuck pixels
• On white, look for black dots — those are dead pixels
• Step through red, green and blue to catch a single failed sub-pixel
• Check gradient for banding and grid for sharpness
• Press Esc when you are finished