Screen testing tools

Screen testing tools is the tool on this page. The control sits above this text. Use it on the display you want to judge, then read what the result can and cannot mean. The target phrase people search is tied to this job, and the explanation below stays with that job instead of repeating a generic review of every display ever made.

These pages fill the browser with a known picture: a solid color, a gray field, a ramp, a contrast bar, a moving block, or a touch grid. The job is to make one kind of defect obvious. Red, green, and blue separate the subpixels. White shows dark defects and dirt. Black shows stuck pixels and, on an LCD, backlight leak. Mid gray shows clouds and dirty-screen effect that a colorful photo hides.

Banding in a gradient is a step between two shades that should have been smooth. It is common on 8-bit output. Dithering can hide it and can also shimmer. Screenz does not decide which you are seeing. It gives you the ramp, full width, so the steps are not a thumbnail. Gamma patches put a fine checker next to a flat gray. If they do not blend at arm's length, the tone curve is far from the 2.2 the patch assumes. A calibrator measures the curve. This page only demonstrates the mismatch.

The refresh counter uses requestAnimationFrame. It counts pictures the browser successfully presented. A 240 Hz panel in a 60 Hz desktop mode will read 60, and the page is right about the mode. Touch testing lights a grid where your finger lands. A mouse can click it, but the test is for a touchscreen, including the inner and cover glass of a foldable. Missed cells along a hinge are a reason to look again with a dry finger and without a thick protector.

Burn-in and image retention are not the same afternoon. Retention fades. Burn-in stays. A moving block will not heal a worn OLED, and a website cannot age your panel on purpose. The moving field is there so a static logo in the bezel of your vision is easier to notice, and so you remember not to leave a paused HDR menu on an OLED overnight.

Screenz is a set of pictures and arithmetic for the display you already have. The picture is drawn by the browser. The arithmetic is the same formula a spec sheet uses, written out so you can change the inputs. Neither one is a laboratory certificate. A dead pixel you can see is real. A refresh number that does not match the sticker is a clue about the operating system, the cable, the battery mode, or the browser, not an automatic failure of the panel.

Use fullscreen when you are hunting a mark. The address bar, the notch, and the rounded corner all hide the edge, and the edge is where a bad pixel and a fold crease like to sit. On a phone, turn the brightness up and turn off the reading tint. On a monitor, leave the preset you actually use, then repeat the test in the neutral preset if you are judging color. Night shift, f.lux, and vivid modes are fine for the evening and misleading for a test.

Dust sits on the glass and moves when you tilt the panel. A dead subpixel stays dark. A stuck subpixel stays lit, so it shows on black. A crease on a foldable is a hinge in the stack. It is not a dead pixel, and a flat color shows it more honestly than a photograph. Pressure spots and backlight bleed on an LCD change with the angle of your head. OLED black should look off, except at the camera hole and along a fold.

The browser cannot measure nits, cannot read EDID on most pages, and cannot promise that a 10-bit ramp is being sent as 10-bit. If a gradient shows steps, the steps may be the panel, the operating system, or the compositor. If a refresh counter reads 60 on a 144 Hz monitor, check the cable, the power plan, and the display setting before you blame the page. Screenz will say this again because it is the difference between a useful test and a false warranty claim.

Photographing the panel with a second phone adds moiré and makes uniformity look worse than it is. Trust your eye at the distance you actually sit. Move closer only to confirm that a mark is in the pixels rather than on the glass. Then wipe the glass and look again. A foldable should be checked twice, cover display and inner display, because they are different diagonals, different pixel densities, and often different aspect ratios.