Screen Test

How to use it

1. Set your browser zoom to 100% and turn off night light, blue light filters and any dynamic contrast or eco picture mode, so you test the screen and not the settings.
2. Press Start full screen (or F).
3. Go to the next test with the right arrow, space, or a tap on the right side of the screen. The left arrow or a tap on the left goes back.
4. Move the mouse or tap to see the name of the test and what to look for. I hides that box, Esc exits.
5. Want it hands free? Pick an auto advance time and it steps through on its own.

What the tests check

• Solid colors: dead pixels (dark dots), stuck pixels (a dot of the wrong color) and dust. The dead pixel test has the same colors plus a tool to mark each one you find.
• Grays: uniformity. Darker corners, bands, tinted areas and the smudgy look called dirty screen effect show best on mid and dark gray. Dark gray is also where burn in shows.
• Gradients: banding, the visible stripes you get when a screen or its settings cannot show a smooth blend.
• Levels and gamma: whether the darkest and brightest shades are visible (black and white level) and whether mid tones are the right brightness (gamma).
• Sharpness and geometry: fine lines and small text for scaling blur and oversharpening, edge lines for overscan, a circle for the aspect ratio, and dots on black for blooming on local dimming screens.
• Reference: SMPTE color bars and our own test card.

Motion is not a still image, so it has its own pages: the refresh rate test and the motion blur and ghosting test.

How to check for backlight bleed

Backlight bleed is light from an LCD backlight leaking past the edges of the panel. It shows as brighter patches along the edges or in the corners of a black screen. Clouding is the same idea in the middle of the screen: blotchy lighter areas.

1. Make the room dark and set the screen to its normal brightness (or full brightness to exaggerate it).
2. Open the Black test and look straight at the screen from your normal seat.
3. Then look from a little further back. A silvery glow that changes when you move your head is IPS glow, a property of that panel type. Bleed stays in the same place whatever your angle.

A little bleed in a pitch dark room is common on LCDs, especially on edge lit screens. Bleed you can see during normal use with the lights on is worth raising with the seller. OLED screens have no backlight, so they cannot have bleed.

Found a problem? What to do next

• Stuck pixel (always one color): try the stuck pixel fixer. It sometimes brings them back.
• Dead pixel (always dark): software cannot fix it. Note where it is, take a photo and check the return window and the maker's pixel policy, since some policies only cover a minimum number of faulty pixels.
• Faint shapes on gray: see the burn in test to tell temporary image retention from burn in.
• Crushed blacks or clipped whites: usually a setting, not a fault. See the black level test.
• New screen with heavy bleed or blotches: returns are easiest in the first days, so test a new monitor or TV straight away.