Screen test
Full-screen patterns for checking a new monitor, phone or television — while you can still send it back. Run through all of them, or pick the one you need.
space or → next · ← back · F full screen · A move on by itself · H hide the box · esc finish
- Full screenThe patterns cover everything else. Press esc whenever you want to come back here.
- A clean screenWipe it first. Dust and smears look exactly like a dead pixel.
- A dark roomHalf of these are about light where there should be none.
- Warmed upGive it twenty minutes switched on before judging brightness or colour.
- No zoomThe finest patterns only mean anything at the screen's real resolution.
Solid colours
One colour at a time, filling the screen. This is how you find a pixel that has died or got stuck, and it is the first thing to do with a screen you might still return.
Even lighting
Flat greys, which show up patchiness that solid black and white both hide. Step back a metre and let your eyes go soft — you are looking for large vague patches, not single dots.
Light and dark
How your screen handles the steps between black and white. This is where settings turned up too far give themselves away, and most of what these find can be fixed from the screen's own menu.
Fine detail and movement
Patterns drawn one real pixel at a time, and bars that move. These only mean something at the screen's own resolution, so make sure the browser's zoom is at 100% before you trust them.
Trying to fix a stuck pixel
A pixel that is stuck on one colour is sometimes only jammed, and can be worked loose. A dead one — always black — cannot be brought back this way.
This one flashes quickly. Skip it if flashing light is a problem for you. It is left out of the full run, and only starts when you choose it here.
Technical details
- Dead, stuck and lit pixels
- A dead pixel never lights and stays black on every colour. A stuck pixel is jammed on and shows as a coloured or white dot on black. Stuck ones sometimes free themselves; dead ones do not. Manufacturers allow a certain number of either before they call a screen faulty.
- Backlight bleed and IPS glow
- Both are the glow on a black screen. Bleed is light escaping around the edges of the panel and stays put as you move. Glow is the panel type showing its angle, and fades or shifts as you move your head — it is normal, and not a fault.
- Mura, and the dirty screen effect
- Faint blotches or vertical bands, easiest to see on a dark grey field or on a slow pan across a football pitch. Almost every panel has some. It matters when you can see it in the things you actually watch.
- Banding
- A smooth gradient breaking into visible steps. It can come from the panel, from the graphics settings, or from the video itself, so check the same clip from another source before blaming the screen.
- Black crush and clipping
- Shades near black merging into one black, or shades near white merging into one white. Usually brightness, contrast, or a mismatch between the limited and full signal range that computers and televisions each prefer.
- Pixel inversion
- Screens flip the voltage across each pixel every frame to stop the liquid crystal degrading. When the flipping falls into step with a single-pixel pattern you get shimmer, flicker, or a drifting moiré — which is what the checkerboard and line patterns look for.
- Response time, ghosting and overdrive
- How long a pixel takes to change. Too slow and moving edges smear behind themselves. Overdrive pushes the change harder to fix that, and pushed too far it overshoots, leaving a bright halo in front instead.
- Real pixels
- The fine patterns are drawn straight onto a canvas the size of the display in real device pixels, so a one-pixel line is one pixel of your screen rather than a scaled approximation. Browser zoom, or a screen not running at its native resolution, breaks that and makes those three patterns meaningless.
- The refresh rate figure
- Counted from frames the browser actually delivers, over the last half second. It is a measurement of the whole chain — screen, cable, graphics card, browser — and browsers throttle it in their own ways, so the highest figure any browser gives you is the closest to the truth.
- This window
- —