Backlight Bleed Test

Dim the room, press Go full screen and look along the edges of the black for light leaking in.

Colour Go full screen, then tap or click for the next one.

What to look for

F goes full screen. Escape leaves.

Black for the edges, level 0

Black for the edges, level 0

#000000 · 0 percent of full light

Every pixel sent zero, #000000. On an LCD the backlight is still on behind it, so any light that escapes round the edges shows as a pale streak or a bright corner. This is the field for the test.

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What to look for

What you might see

Doing the test fairly

What then

Next step Eyes adjusted? Hunt dead pixels on six coloursPlain black for other uses, full screen

All 14 fields and checks

Fields to show 3

  • Black for the edges, level 0 Every pixel sent zero, #000000. On an LCD the backlight is still on behind it, so any light that escapes round the edges shows as a pale streak or a bright corner. This is the field for the test.
  • Dark grey for strong bleed, level 24 #181818, about 0.91 percent of white's light. Faint bleed disappears once the whole field is lit a little. Bleed that still shows on this grey is strong enough to notice in dark scenes of films and games.
  • Mid grey to rule out bleed, level 96 #606060, about 11.7 percent of white's light. Bleed is hard to see on a field this bright. A patch that stays on this grey is not bleed but uneven lighting, which the gray uniformity test checks.
Show all 14 fields and checks (11 more)

What you might see 5

  • Blotches away from the edges Soft patches in the body of the screen rather than at its border are clouding. It is common on curved VA monitors and usually visible only in very dark scenes. Compare it on the dark grey field.
  • Bright patches in the corners Wedges of light spreading inward from one or more corners, as if a torch were pointed at the glass from behind. This form of bleed is called flashlighting.
  • Glow that changes as you move A haze that brightens, fades or slides when you move your head or change the lid angle is panel glow, best known on IPS screens. Unlike bleed, it changes with angle, distance and the light behind the screen.
  • No bleed on an OLED screen An OLED has no backlight: each pixel makes its own light and a black pixel is switched off. A phone or television with an OLED panel cannot show backlight bleed, so light at its edges on black means something else.
  • Pale streaks along an edge Light leaking round the border of the panel, the classic form of backlight bleed. It stays in the same place wherever you sit, and it is brightest on the black field.

Doing the test fairly 4

  • Brightness where you keep it Judge first at the brightness you use every day, because that is the bleed you will live with. Then try full brightness: bleed grows with the backlight, and lowering brightness is the simplest way to make it less noticeable.
  • Let your eyes adjust for a minute Turn the room lights off and wait a minute or two before you judge. Eyes grow more sensitive in the dark for many minutes, so faint bleed appears gradually and a first glance can miss it.
  • Photograph it fairly A camera on automatic brightens a dark scene until bleed looks far worse than it is. Lower the exposure until the photo matches what your eyes see, then take it straight on from your normal seat.
  • Straight on, at your usual distance Sit where you normally sit with your eyes level with the middle of the screen. Looking from close up or from an angle adds glow that is not bleed and makes every corner look worse.

What then 2

  • Check the rest of the panel too While the screen is dark and your eyes are adjusted, look for lit points on black as well. Then run the dead pixel and uniformity tests so any return request covers everything at once.
  • Some bleed is normal A little bleed is expected on an LCD, and most of the time it does not show in ordinary pictures. Whether yours is bad enough to return is set by the seller's or maker's policy, so read it before the return window closes.

How this list was compiled: Fields and checks written for this page. Light shares are relative luminance computed from the sRGB transfer function at https://en.wikipedia.org/wiki/SRGB, with white as 100. Backlight bleed as light leaking round the edges or corners of an LCD, its forms clouding and flashlighting, clouding being common on curved VA monitors and mostly visible in very dark scenes, OLED panels not suffering from it, lowering brightness to make it less noticeable, and IPS glow changing with viewing angle, distance, brightness and light behind the screen: https://www.displayninja.com/what-is-backlight-bleed/. An LCD's backlight staying lit behind a black picture: https://en.wikipedia.org/wiki/Liquid-crystal_display. An inactive OLED pixel giving no light: https://en.wikipedia.org/wiki/OLED. The eye growing more sensitive in the dark over 20 to 30 minutes: https://en.wikipedia.org/wiki/Adaptation_(eye). A light meter overexposing a mostly dark scene: https://en.wikipedia.org/wiki/Exposure_compensation. All read 2026-09-24. That faint bleed fades once the field is lit is this page's own explanation: bleed adds a fixed amount of light, which matters less the brighter the field. Licence: own work

How it works

This backlight bleed test fills the screen with black, where LCD screen bleeding, light escaping round the edges, shows as pale streaks or bright corners. After the black, step on to the two greys.

Read the full guide

Bleed, glow or clouding

Bleed stays put when you move your head. Glow, best known on IPS screens, shifts with your angle. Clouding sits in the middle, not at the edges. A screen bleeding test on an OLED phone finds nothing: it has no backlight.

Two greys tell you how strong

If bleed vanishes on Dark grey for strong bleed, level 24, it will seldom show in films or games. If it survives, it will. A patch still there on the mid grey is uneven lighting, not bleed.

  • Wait a minute in the dark before you judge: your eyes keep growing more sensitive, and faint bleed appears slowly.

Questions and answers

Is a bleeding monitor test the same as a black screen?

Almost: both show black. This page adds two greys to judge how strong the bleed is, and checks to tell it from glow and clouding. For a plain black screen for other uses, open the black screen.

Can backlight bleed be fixed?

Not completely. Lowering the brightness makes it less noticeable. If it bothers you in normal use, ask the seller or maker about a return while you still can; a replacement can have bleed of its own.

What does a monitor bleed test show on an OLED?

Nothing, because an OLED has no backlight: a black pixel is switched off. On an OLED, look for uneven near-black greys instead with the AMOLED grey uniformity test.

How to test backlight bleed on a new screen?

A screen bleed test needs a dark room, your usual brightness and the black field full screen. Sit straight on at your normal distance, eyes level with the middle of the screen, and look along each edge and into each corner.

Is this light bleed test also an IPS glow test?

Yes, the same black shows both. Glow is strongest close up and from an angle, so sit back and straight on: what fades is glow, and what stays is bleed.

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