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Backlight Bleed Test

Use this backlight bleed test to check an LCD monitor, laptop or TV for light leaking at the edges. Dim the room, press Start and look for bright patches on the black screen.

Before you start
Black → 2% → 5% → 10% → 25% → white · Esc exits

Not sure? Most monitors and laptops use an LCD panel (IPS, VA or TN). The spec sheet tells you which.

Give your eyes about a minute in the dark before you judge. On a laptop, turn off brightness that changes with content.

Settings
Levels to show

How to do a backlight bleed test

  1. Darken the room. Turn off the lights and any other screens. Room light hides faint bleed.
  2. Set your usual brightness. Judge the screen at the level you really use. Then try 100% to see the worst case.
  3. Press Start test and wait about a minute. The screen turns black, and your eyes need time to adjust to the dark.
  4. Look straight at the screen from your normal viewing distance. Note any bright patches at the edges and corners.
  5. Step through the grays. Press → or tap the right side. The 2%, 5%, 10% and 25% grays show clouding and dark corners.
  6. Move your head to the side, then step back. Watch whether the bright areas change.

Press Esc to finish. Mark where you saw light and answer 3 questions, and the backlight bleed test tells you what you found.

Your eyes keep adapting to the dark for many minutes. Faint glow looks stronger the longer you stare, so trust what you see in the first few minutes.

What is backlight bleed?

Backlight bleed is light from an LCD’s backlight leaking around the edges of the panel, seen as bright patches on dark images. It comes from uneven pressure where the frame holds the panel layers, and from small gaps left during assembly. Edge-lit screens, with LEDs along one or more sides, often show it most.

On a black screen, bleed looks like a whitish or yellowish haze that starts at an edge and fades toward the center. It can affect any LCD: IPS, VA and TN panels alike. OLED screens have no backlight, so they can’t bleed.

A backlight bleed check is sometimes called a screen bleed test. Single bright dots are a different problem: those are stuck or hot pixels, and the dead pixel test finds them.

Backlight bleed vs IPS glow vs clouding

All three show up as light on a dark screen, but they act differently when you move.

Diagram: bleed at fixed edge spots, IPS glow in corners that shifts with angle, clouding as patches in the middle Backlight bleedfixed spots at the edgesIPS glowcorners, shifts as you moveCloudingpatches away from the edges
How each problem looks on a black screen in a dark room. Glow changes when you move your head; bleed and clouds stay put.
Backlight bleed IPS glow Clouding
Where it appears Fixed spots at the edges or corners Corners, strongest from an angle Patches away from the edges
Changes when you move? No Yes: it shifts, grows or fades No
Panel types Any LCD IPS Any LCD, most often large or edge-lit screens
Normal? Mild bleed is common Yes, on IPS panels Mild clouding is common
What to do Return or exchange if you see it in normal use Sit centered, and add a light behind the screen Exchange if it shows in dark movies or games

IPS glow comes from the way IPS panels leak a little light at steep viewing angles. The corners you see at the steepest angle glow most, so the glow moves when you move. Bleed and clouds stay in the same place.

Monitor uniformity test: clouding and dark corners

The gray steps turn this page into a monitor uniformity test. A perfect screen shows each gray as one flat, even color, but real screens vary a little.

  • 2% and 5% gray show clouding: blotchy, lighter patches across the middle.
  • 10% and 25% gray show dark corners (vignetting) and tint, such as a pink or green cast on one side.
  • White shows brightness falloff toward the edges and dust trapped behind the panel.

Some screens show the “dirty screen effect”: faint bands or smudges you notice when a game pans across a flat color. Screens with local dimming switch dark zones off on pure black, so judge them on the 2% gray. On an OLED screen, the same grays work as an OLED uniformity test for banding and uneven near-black. For colors, gradients and sharpness, run the full monitor test.

Understanding your results

Result What it means What to do next
Looks good: no bleed seen Your screen looks even in the dark. Nothing. Keep the screen.
Looks good: IPS glow Normal corner glow for an IPS panel. Nothing. Sit centered and add bias lighting if it bothers you.
Possible issue: mild bleed or clouding Common on LCDs, and visible only in a dark room. Check again at your usual brightness. Keep the screen if you don’t notice it in normal use.
Possible issue: strong IPS glow Normal behavior, but more than some units show. Compare with another unit if it bothers you.
Problem found: noticeable bleed or visible clouding You can see it in normal use. Consider a return or an exchange while the window is open.

Copy report saves your answers, the panel type and the screen size. Paste it into a return request or a support ticket.

Can backlight bleed be fixed?

Usually not at home. The real fix for backlight bleed is a return or an exchange while the store’s window is open. Two units of the same model can differ a lot, so an exchange is a fair try.

You can make bleed less visible:

  • Lower the brightness. Bleed fades as the backlight dims.
  • Add bias lighting. A soft light behind the screen makes the edges look darker.
  • Leave some room light on for dark movies and games.

Some online guides suggest loosening the back-panel screws or massaging the edge of the panel. We don’t recommend either on a new screen. Pressure can crack the panel, and opening the case may void the warranty.

Some owners report that bleed changes a little over the first weeks as the panel settles. Don’t count on it: decide inside your return window. Few brands publish a rule for bleed itself, and LG, for example, calls light leak seen from a steep angle normal.

Before you file a warranty claim, read your brand’s display policy: Dell, LG, Samsung (in German), ASUS, Acer, Apple or Lenovo.

Testing a laptop, TV or phone

A monitor backlight bleed check works as described above. Laptops, TVs and phones need a few changes.

Laptop backlight bleed test

On laptops, bleed often shows along the bottom edge near the hinge. Before you test, turn off auto-brightness, which dims the screen in a dark room, and any setting that dims the backlight on dark content. Then run the test with the lid at your usual angle.

On Windows 11, both are in Settings › System › Display › Brightness: turn off Change brightness automatically when lighting changes, and set Change brightness based on content to Off. On a Mac, turn off Automatically adjust brightness in System Settings › Displays.

TV backlight bleed test

Open this page in the TV’s browser, or connect a laptop over HDMI. Local dimming and dynamic contrast hide bleed on pure black. Check the 2% gray with local dimming on, which is closer to what you see in films.

Phone backlight bleed test

Phones with LCD screens can bleed too, including LCD iPhones such as the iPhone XR, 11 and SE models. iPhones with OLED screens can’t. Turn off auto-brightness, turn the phone to landscape and tap the right side of the screen to step through the levels.

Taking a photo of backlight bleed

Phone cameras exaggerate bleed. Auto exposure brightens a dark scene, so faint glow turns into bright white blobs. For a fair photo:

  • Use pro or manual mode, and lower the exposure until the photo matches what you see.
  • Turn off night mode.
  • Take a second photo with the room lights on, on a dark scene, to show how it looks in normal use.

Frequently asked questions

How do I test for backlight bleed?

Darken the room, set your usual brightness and open a full-screen black image, such as this backlight bleed test. Wait about a minute so your eyes adjust, then look at the screen from your normal distance. Check the edges and corners for bright patches, step through the dim grays, and move your head to tell bleed from IPS glow.

Is backlight bleed normal?

Some backlight bleed is normal on LCD screens. Most LCDs let a little light escape at the edges, which you can see on a black screen in a dark room. It becomes a problem when you notice it in normal use: with room lights on, while watching a dark movie or playing a dark game. Then a return or an exchange is worth asking for.

What does backlight bleed look like?

Backlight bleed looks like bright, often whitish or yellowish patches on a dark image. The patches start at the edges or corners of the screen and fade toward the middle. They stay in the same place when you move your head, which sets them apart from IPS glow. You see them best on a black screen in a dark room.

Should I worry about backlight bleed?

Only if you see it in normal use. Mild bleed that shows only on a black screen in a dark room is common on LCDs. If you notice it in dark movies or games with the lights on, it will probably keep bothering you. Decide while your return window is still open, because a store exchange is usually easier than a warranty claim.

Can screen bleed go away?

Rarely. Some owners report small changes over the first weeks as the panel settles in its frame, but you shouldn't expect bleed to disappear. Don't wait for it to fade. Run the backlight bleed test early, save the report, and decide while you can still return or exchange the screen.

Do OLED TVs have backlight bleed?

No. OLED TVs have no backlight: each pixel makes its own light and turns fully off for black. That means they can't show backlight bleed, IPS glow or LCD clouding. They can show other near-black problems, such as uneven dark gray, banding or burn-in. Use an OLED burn-in test with dark gray screens to check for those.

How do I test screen uniformity?

Show a full-screen gray and look for differences across the screen. Use 5% and 10% gray for clouding, 25% gray for dark corners and tint, and white for brightness falloff toward the edges. Test in a dim room at your usual brightness. This page includes all of these steps, so you can run a screen uniformity test right after the bleed check.

What causes backlight bleed?

Backlight bleed comes from how an LCD is built. The backlight sits behind several thin layers held in a frame. Uneven pressure from that frame, small assembly gaps and edge-lit designs, where LEDs shine in from the sides, let light escape at the edges. That's why two units of the same model can differ a lot.

  • Dead Pixel Test

    Full-screen solid colors (white, black, red, green, blue, cyan, magenta, yellow, gray) to spot dead, stuck and hot pixels and more.

  • Black Screen

    One-click full-screen pure black with a timer, dim-to-black, an optional clock overlay and a keep-awake toggle.

  • Stuck Pixel Fixer

    Flashes a small, movable, resizable RGB noise square over a stuck pixel for 10-60 minutes to try to revive it.

All monitor tests

Written and tested by Tanveer Azam Ansari. I check each tool by hand on real monitors, keyboards, mice and controllers in current desktop and phone browsers before it goes live.

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