Fills the screen with pure black so you can see light leaking through it. Before you use it, one warning: most people who run this test end up worried about a monitor that is fine, and the reason is almost always the camera.
F to start, Esc to exit
How to run it
1
Kill the room light
Bleed is not judgeable with the lights on. Any ambient light raises your eye’s adaptation level and hides it.
2
Wait a full minute
Your eyes need roughly that long to dark-adapt. Judging in the first ten seconds overstates the leak every time.
3
Set your real brightness
Not maximum. Whatever you actually work at, because that is the only condition that matters.
4
Look at the edges, straight on
Bleed is an edge phenomenon. Something in the middle of the panel is a different problem.
Field notes
Photographs of backlight bleed are lies.
This is the single biggest reason people return healthy monitors, and I would put it above every other note on this page.
Point a phone at a black screen in a dark room and it picks a long exposure and a high ISO, because that is what it is built to do. The leak comes out several times brighter than your eye sees it. Every comparison photo posted online is subject to the same distortion, so a panel that "looks worse than the ones on Reddit" may well be identical in person.
Judge with your eyes, from where you actually sit. Use a photo only to document something you can already see unaided.
Not a photograph. A simulated leak, at a fixed intensity that never changes. Only the gain moves. A phone pointed at a black screen in a dark room chooses something near the right end of that slider on its own, which is why the bleed photos people post look so much worse than the panel does in the room. Judge the panel, not the picture of it.
Last checked 2026-08-04
IPS glow is not bleed, and it is not a defect.
Lean left. If the glow on the right grows, and leaning right swaps it, that is IPS glow: a property of how IPS panels polarise light off-axis. Every IPS panel has it, and no replacement unit will be free of it.
Backlight bleed does not move. Same place, same brightness, whatever angle you look from. That head-tilt is the whole test.
Last checked 2026-08-04
Pressure marks come from the frame, not the backlight.
A tight bezel or an over-torqued screw squeezes the LCD stack and produces a bright bar or a distinct blob, usually along one edge. It reads harder-edged and more localised than diffuse bleed. Some monitors settle over a few weeks as the assembly relaxes. Some never do.
Do not try to fix it by pressing on the panel. That is a reliable way to turn a small complaint into a permanent one.
OLED cannot have backlight bleed. There is no backlight.
Each pixel emits its own light, so black is genuinely off. If you are running this on an OLED and the field is uniform, that is the expected result and the test has nothing more to tell you. What OLED can show on black instead is faint vertical banding at very low brightness, and retained images from static interface, which is the burn-in test’s job.
Written by Mor. If a panel of yours behaves differently, tell me and I will correct it.
Questions
Other tools
White Screen Test Check a white field for dust, dead pixels, uniformity, and tint.
Dead Pixel Test Cycle white, black, red, green, and blue to find faulty pixels.
Stuck Pixel Fixer Rapidly flash colors over a stuck pixel to try to un-stick it.
Screen Burn-In Test Reveal retained images and uneven wear on OLED and plasma panels.
Monitor Test Full sweep: pixels, bleed, uniformity, and color channels.
Light Box Use the screen as a tracing panel or soft photography light.