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Backlight Bleed Test

A pure black screen for finding light leaking around the edges of a panel. Turn the room lights off first — this test is meaningless in a lit room.

Backlight bleed only shows on a fully black screen in a dark room. Start the test, turn the lights off, and give your eyes a minute to adjust.

Press F for fullscreen, Esc to exit.

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What the backlight bleed test shows

Backlight bleed is light escaping past the edge of the LCD layer, usually from clamping pressure in the frame. It looks like patches or streaks of lighter grey, most often in the corners, and it does not change when you move your head.

IPS glow is different and is constantly confused with it. Glow is a silvery, often slightly warm haze in the corners that changes as you move — lean left and the glow moves to a different corner, or disappears. It is inherent to how IPS panels work and it is not a fault. Bleed stays put; glow follows you.

How to test backlight bleed correctly

Turn off every light in the room and close the curtains. Then wait: your eyes take several minutes to adapt to darkness, and a test run thirty seconds after turning the lights out will find bleed that is not really there at any normal brightness.

Set the monitor to the brightness you actually use, not maximum. Bleed at 100% brightness in a pitch dark room is a photograph people post online; bleed at your working brightness is the thing that affects you.

Move your head from side to side. Anything that moves or fades is IPS glow, not bleed.

What this test cannot tell you

Photographs make bleed look far worse than it is, because a camera exposing for a black screen brightens everything. Judge it with your eyes at your normal brightness, not through a phone.

Questions

What is the difference between backlight bleed and IPS glow?

Bleed is light escaping past the panel edge — patches or streaks that stay in the same place whatever angle you view from. IPS glow is a silvery haze in the corners that moves or disappears as you shift your head. Bleed can be a defect; glow is how IPS panels work.

How much backlight bleed is acceptable?

Almost every LCD has some. The practical test is whether you can see it during normal use at your normal brightness — in a dark room at maximum brightness, essentially every panel looks bad.

Can backlight bleed be fixed?

Sometimes it improves over the first few weeks as the frame settles. Beyond that it is a hardware matter, and if it is bad enough to see in normal use it is worth a warranty claim rather than a home remedy.

Is the backlight bleed test free?

Yes — free, with no account, no download and no limit. It is a web page, so it runs on any device with a modern browser.

Do I need to be fullscreen?

For anything involving the whole panel, yes. Press F, or the fullscreen button. On a desktop browser F11 also hides the browser toolbars, which matters for the tests where a bright strip at the top of the screen would affect what you are looking at.