Backlight Bleed Test

Fill your screen with black and two near-black shades to see whether light leaks in from the edges. Free, instant, and nothing to install.

How to test

  • Make the room as dark as you can — bleed hides in daylight.
  • Turn the screen's brightness up to maximum.
  • Look at the screen straight on — from an angle, even a good screen glows.
  • Give your eyes a minute to get used to the dark before judging.

How to Read a Backlight Bleed Test

The test fills your screen with black and two very dark grays — the shades where uneven lighting has nowhere to hide. Here is what you might see, and what each thing means.

What backlight bleed looks like

On a black screen, backlight bleed shows up as patches of light creeping in from the edges or corners, as if a flashlight were shining from behind the frame. It comes from the panel's backlight escaping where the layers are pressed together unevenly, and it sits in the same spots no matter how you look at the screen. You'll notice it most in dark movie scenes and games at night.

Backlight bleed or IPS glow?

Before judging your screen, rule out its harmless twin. IPS glow is a soft sheen — often silvery or slightly golden — that appears when you look at a dark screen from an angle. The giveaway: move your head side to side. Glow shifts, fades or disappears as your angle changes; true bleed stays exactly where it is. Nearly every IPS screen glows a little, and it is not a defect.

Clouding — the blotchy cousin

Clouding is the third look-alike: irregular brighter blotches floating in the middle of the screen rather than at the edges. On this test it is easiest to catch on the two dark gray screens, where the clouds stand out against what should be a perfectly even shade. A little clouding is common on large TVs; heavy, distracting clouds on a new screen are a fair reason to swap it.

Which screens are affected

Bleed can only happen on screens with a backlight — that is, LCD screens, which includes most monitors, laptops and budget TVs. OLED screens cannot bleed: each of their pixels makes its own light and simply switches off for black. If a black screen on an OLED shows glowing patches, that is a different problem — worth checking with the burn-in test.

When it's worth a return

Some bleed is considered normal by most manufacturers, so a faint corner glow rarely qualifies for a warranty claim. What tips the scale: bleed you can see at normal brightness in a lit room, bleed that distracts you in dark scenes, or a bright streak across a large area. For a brand-new screen, test it within the return window — a straight return is far easier than a warranty case.

Can it be fixed?

Honestly: usually not. Bleed comes from how the panel was assembled, so there is no setting that removes it. Lowering brightness makes it less visible, and on some monitors very gently loosening or re-seating the frame has helped — but that is a lottery and can make things worse. If the bleed bothers you on a new screen, an exchange is the realistic fix.

Check for dead pixels too
Cycle solid colors across the screen to catch pixels that are stuck on one color or always dark.
Find dead pixels
OLED screen? Test for burn-in
Solid color screens reveal ghosts of old images that stay burned into the picture.
Check for burn-in

Frequently asked questions

Darken the room, turn the screen's brightness up, and start the test — it fills the screen with black. Look along the edges and corners from straight ahead: any patches of light leaking in from the frame are backlight bleed. Click through to the dark gray screens too; blotchy unevenness shows up better there.
Move your head. That is the whole trick: IPS glow — a soft sheen most dark screens have — moves, fades or vanishes as your viewing angle changes. Backlight bleed stays fixed in place no matter where you look from. Glow is normal physics of the panel; bleed is light escaping around its edges.
A small amount is, unfortunately, normal for LCD screens — perfectly sealed panels are rare, and most manufacturers accept faint bleed as within spec. The question is whether you can see it in real use: if dark movie scenes at normal brightness show obvious bright patches, that is more than you should put up with on a new screen.
It can. Heat and the pressure of the frame can shift the panel's layers slowly, so bleed sometimes grows over months or years. It can also appear after a knock or after the screen has been carried around. That is one more reason to test a new screen right away, while returning it is still simple.
There is no reliable fix. Reducing brightness hides it, and repositioning a slightly warped frame occasionally helps on monitors, but nothing you can click will remove it — the light is physically escaping around the panel. If it bothers you, exchange the screen while you can.
No — OLED screens have no backlight to bleed. Every pixel lights itself and turns fully off for black, which is why OLED black looks bottomless in a dark room. OLED has its own weakness instead: permanent image retention, which you can check with the burn-in test.