Monitor Test — Dead Pixels, Bleed and Banding

Monitor Test fills your screen with the patterns people use to inspect a display, one after another, and says on each what a fault looks like. Solid black, white, red, green and blue find dead pixels (dots that stay dark) and stuck pixels (dots that stay one colour); black in a dark room shows backlight bleed and IPS glow at the edges; mid and dark grey show uneven brightness and clouding. Smooth gradients reveal banding, where a screen shows steps instead of a smooth ramp. The black-level and white-level patterns have sixteen squares just above black and just below white: the more you can tell apart, the more shadow and highlight detail the screen keeps. The sharpness pattern draws lines and a checkerboard exactly one screen pixel wide, so blur or moiré means the screen is not at its native resolution or the page is zoomed; the text pattern shows small sizes for fringing. The motion pattern moves white blocks across black at three speeds, timed so a dropped frame shows as a jump and slow pixels as a trail, with the frame rate the browser is actually drawing. Use the arrow keys, a tap or the buttons to step through; the hint hides itself so the pattern is clean. Afterwards tick what you found and copy a short note for a return, a warranty claim or a second-hand listing. Use it on a new monitor or laptop inside the return window, on a TV through a laptop, or on a phone or tablet.

1. Clean the screen, set the brightness you normally use, and for bleed darken the room.
2. Press Start the full test, or pick one pattern.
3. Step with → or a tap, back with ←; Esc ends. H hides the hint.
4. Tick what you saw and copy the note.

• A person judges the result: the page cannot see the screen. Look closely, and use a magnifier for very small pixels.
• There is no flashing “stuck pixel fixer”: rapidly flashing colours can trigger seizures, and they rarely revive a pixel.
• Full screen is not available for web pages on iPhone; the patterns fill the window instead, so hide the toolbars.
• Motion clarity depends on the browser keeping up; close other tabs for the truest result.
• The patterns are drawn in your browser and the page works offline. Nothing is uploaded or saved.

A dead pixel stays black on every colour: no light passes. A stuck pixel stays one colour (often red, green or blue). Stuck pixels sometimes recover; dead ones do not.

It depends on the maker’s pixel policy (ISO 9241-307 classes). Many allow a few; some promise none. Check the warranty, and test inside the return window.

A little glow at the corners on a black screen in a dark room is common on IPS panels. Bright patches visible in normal use, or bleed that shows on dark films, is worth reporting.

The browser dropped frames: the computer was busy, a power saver is on, or the screen runs at a lower rate than you think. The frame rate shown is what the browser is actually drawing.