Screen Bleeding Test
Check your display for backlight bleed, corner glow, IPS glow, and clouding. The test fills your whole screen with pure black — turn off the lights, then look along the edges and corners for any light leaking through. While you're at it, the Dead Pixel Tester catches dead and stuck pixels too.
← → change level · Esc exit
Bright light leaking from the edges and corners — stays fixed when you move your head.
A warm corner glow on IPS panels that shifts and fades as your viewing angle changes.
Uneven blotchy patches across the panel, easiest to see on the near-black grey screens.
How it works
An LCD makes black by twisting its liquid crystals to block a backlight that's always switched on — but the blocking is never perfect. Where light slips past the panel layers, usually at the clamped edges and corners, it reaches your eyes as a faint glow. A full black screen in a dark room is the harshest possible background for that leak, so any bleed, glow, or uneven clouding stands out against the surrounding black. The near-black grey screens help too: a touch of brightness can make broad, blotchy mura easier to see than pure black does.
Bleed vs IPS glow vs clouding
- Backlight bleed— bright light leaking at the edges or corners that stays fixed as you move your head. Some is normal; large patches aren't.
- IPS glow — a warm corner haze on IPS panels that shifts and fades with your viewing angle. Normal for the panel type, not a fault.
- Clouding / mura — uneven, blotchy lighter areas across the panel, often easiest to see on a near-black grey field.
For an accurate test
- Switch off the room lights — bleed is only fairly judged in the dark.
- Clean the screen first so dust and smudges aren't mistaken for leak.
- Let your eyes adjust for a minute, then view straight-on from a couple of feet back.
- Turn brightness up to reveal faint bleed, but judge how much it bothers you at your normal brightness.
- Move your head around to separate fixed backlight bleed from angle-dependent IPS glow.
- Test a new monitor early, while you're still inside the return window.
Frequently asked questions
What is backlight bleed?
Backlight bleed is light from an LCD's backlight leaking around the edges or corners of the screen, showing up as brighter patches on what should be a uniform black image. It happens because the panel layers can't block the backlight perfectly, especially where they're clamped at the bezel, so a little light escapes. It's only really visible with dark content in a dark room — black movie bars, loading screens, or night-time game scenes — and OLED screens don't have it at all, since each pixel makes its own light.
What's the difference between backlight bleed and IPS glow?
They look similar but have a simple tell: move your head. Backlight bleed is a fixed bright spot, usually at an edge or corner, that stays in the same place and roughly the same brightness no matter where you look from. IPS glow is a wider, warmer haze in the corners of IPS panels that visibly shifts, grows, and fades as you change your viewing angle or distance. If it moves with your head it's IPS glow, which is normal for the panel type; if it stays put it's backlight bleed.
How do I test my screen for backlight bleed?
Turn off the room lights, wipe the screen clean so dust isn't mistaken for leak, and display a full black screen in fullscreen. Give your eyes a minute to adjust to the dark, then look at the screen straight-on from a couple of feet back and scan the edges and corners for any brighter patches. Turning brightness up makes faint bleed easiest to spot; then judge how much it actually bothers you at your normal brightness. Finally, shift your head around to separate fixed bleed from angle-dependent IPS glow.
Is some backlight bleed normal, or is it a defect?
A small amount of backlight bleed is normal on practically every LCD and isn't considered a defect on its own — it's a limitation of how the panels are built. It becomes a problem when it's severe: large, obvious bright patches or flashlighting in the corners that you notice during normal use, not just in a pitch-black room with brightness maxed. Manufacturer thresholds vary, so if bleed is heavy on a new or in-warranty display, document it and check the return or warranty policy.
Can I fix or reduce backlight bleed?
Bleed is a physical panel issue, so there's no software fix, but you can make it less noticeable. Lowering your brightness is the single most effective step, since bleed scales with backlight intensity. Repositioning or slightly tilting the screen can change how much you see, and letting a brand-new monitor run for a few days sometimes eases very mild bleed as the panel settles. Heavy-handed tricks like flexing the bezel risk damaging the panel and are best avoided — if it's severe, a warranty replacement is the safer route.
Do phones, OLED screens, and TVs have backlight bleed?
Any LCD can have it — LCD phones, laptops, monitors, and LED-backlit TVs included — so the test works on all of them in a browser. OLED and AMOLED screens don't have backlight bleed at all, because they have no backlight and each pixel lights itself, giving perfectly uniform black; they have other quirks like burn-in instead. Mini-LED TVs greatly reduce bleed with local dimming but can show blooming around bright objects, which this black-screen test won't stress.