Which test to use
The display tests fall into three groups. The first group fills the whole screen with a solid image so you can look at the panel itself. The dead pixel test steps through seven colours and is the quickest way to find a pixel that is stuck or dark. White screen, black screen and colour screen give you one surface to study for as long as you need: white shows dirt, dark pixels and uneven tint, black shows stuck bright pixels and how deep the blacks go, and a pure red, green or blue lights a single sub-pixel so you can tell which one has failed.
The second group is for faults that only appear in specific conditions. The backlight bleed test uses black and two near-black greys in a dark room, with a thirty-second adaptation timer, to show light leaking from the edges of an LCD. The screen burn-in test loops six colours slowly so that a ghost of a taskbar, a logo or a channel badge becomes visible on an OLED or plasma panel.
The third group measures motion. The refresh rate test counts frames and reports the rate in Hz, which catches a 144 Hz monitor that is quietly running at 60. The FPS test shows frames per second with no load, a medium load or a heavy load, and the motion blur test moves a striped tile across the screen next to a still copy, so you can see smearing and ghosting with your own eyes.
How to get a reliable result
Clean the screen first: a speck of dust looks exactly like a dead pixel on white. Set brightness to the level you normally use, turn off night mode and any blue light filter, and close other heavy tabs before a motion test. For bleed and burn-in, darken the room and let your eyes adjust, otherwise a faint glow will not show. For refresh rate on a laptop, plug in the charger, because battery saving often locks the panel at 60 Hz.
Look at the screen straight on and from arm's length. A glow that moves when you move your head is IPS glow, a property of the panel type, while a patch that stays put is bleed.
What counts as a fault
A single dead pixel in the middle of the screen is worth reporting on a new device. Slight glow in the corners of an IPS panel at full black in a dark room is normal and usually not covered. A refresh rate far below the advertised figure is almost always a setting, a cable or a power mode, so check those before blaming the monitor. Write down what you saw and when, and repeat the same test in front of the shop or the service centre.
Frequently asked questions
Which display test should I run first on a new monitor or laptop?
Start with the dead pixel test, because a defective pixel is the quickest fault to spot and prove, and the return window for a purchase is short. Whether one pixel is enough for an exchange depends on the maker's pixel policy. Then run backlight bleed in a dark room, and finish with the refresh rate test to confirm the panel runs at the rate printed on the box. The three together take under five minutes.
Can a website really measure my screen?
Partly. The refresh rate and FPS tests count the frames the browser actually draws, which is a real measurement, although it is capped by the browser and by power saving. Pixels, bleed, burn-in and motion blur cannot be read back by any web page: those tests put the right image on the panel and your eyes make the judgement.
Do these tests work on phones, TVs and OLED panels?
Yes, they work in any modern browser on any screen, including phones, tablets, smart TV browsers and OLED monitors. The black screen is the best check for OLED, since a true black pixel is switched off. On a TV browser the refresh rate result may read 60 Hz even on a 120 Hz set, because many TV browsers render at 60.
Can the solid colour screens damage my display?
No. A few minutes of a single colour is normal use for any panel, including OLED. Retention and burn-in come from the same bright image held for hundreds of hours, not from a short test. Keep brightness at a comfortable level and exit when you are done; every fullscreen test closes with Esc, the close button or a swipe down.