Backlight Bleed Test

What backlight bleed looks like

LCD screens (most laptops, monitors, TVs and some budget phones) light the picture from behind with a backlight. If the panel isn't sealed perfectly against its frame, some of that light leaks out around the edges. On a black screen in a dark room you see it as brighter, cloudy patches, usually in the corners or along one edge. That is backlight bleed.

OLED screens, used in most recent flagship phones and some laptops, light each pixel on its own and have no backlight, so they can't bleed. On an OLED, pure black should look exactly like the screen turned off. If it doesn't, check for burn-in with the burn-in test instead.

How to run the test

1. Darken the room and set the brightness to maximum. Bleed that is invisible at 50% brightness in daylight is often obvious this way, so don't panic at what you see; judge it the way you'll actually use the screen as well.
2. Tap Start full screen. The first screen is pure black. Tap or press Space to step through very dark gray and dark gray, which show clouding (uneven blotches across the middle) better than black.
3. Look straight at the center from your normal distance. Then move your head to the side: anything that changes color or moves with your viewing angle is IPS glow, not bleed.
4. Press Esc or tap the × to exit.

Bleed, IPS glow or clouding?

• Backlight bleed: light patches fixed at the edges or corners that look the same from any angle. Caused by uneven pressure on the panel, often from the frame or bezel.
• IPS glow: a silvery or orange glow in the corners that changes or disappears when you move your head. It is a property of IPS panels and is normal to some degree.
• Clouding: blotchy, uneven brightness spread across the screen, most visible on dark gray. Common on large LCD TVs and monitors.

Is it a fault?

Almost every LCD has a little bleed if you look for it at full brightness in a pitch-dark room. Manufacturers don't treat that as a defect. It becomes a problem when you can see it during normal use: watching a dark film, or using dark mode at your usual brightness. If a new laptop or monitor shows bright patches that bother you in normal use, return or exchange it within the return window, which is usually easier than a warranty claim. Take a photo with your phone at a similar exposure to what you see, since phone cameras tend to exaggerate bleed.

Checking a used laptop

Bleed that appears in one corner of a used laptop can come from a hinge or lid that was bent or squeezed. Look for gaps between the bezel and the screen, and gently flex the lid while the black screen is showing: bleed that changes as you press means the panel is under strain. Our used laptop checklist covers the rest of the screen, hinge and port checks, and the dead pixel test finds stuck and dead pixels.