Screen Bleeding Test
Fill your screen with pure black, near-black and dark grey to check a monitor, laptop or TV for backlight bleed, IPS glow and clouding. Runs in your browser, nothing to install.
Run the test
Click, Space or the arrow keys step through the four shades. Swipe left or right on a touch screen. The exit button fades so it does not cover the corners. Move the mouse, or press G or Tab, to show it again. G also shows the corner guide. On a touch screen, tap once to show the button, then tap the X. Press Esc to exit. iPhone Safari has no fullscreen mode for web pages, so hide the toolbars or add the page to your home screen for the cleanest view.
Before you start
- Use a dark room. Bleed is easiest to see with the lights low, but don't judge a screen only in pitch black.
- Set brightness to the level you normally use, not 100%. Turn off HDR and dynamic contrast.
- Let the screen warm up for a few minutes and wipe off dust or smudges.
- Look straight on from your usual seating distance first.
- Then move your head to the side and up and down. A corner sheen that changes with viewing angle is IPS glow. Bright patches that stay put are backlight bleed.
- Don't judge from a long-exposure phone photo. Cameras exaggerate bleed far beyond what your eyes see.
Bleed, glow or clouding?
Backlight bleed
LCD panels are lit from behind, and the panel has to block that light to show black. Bleed is light escaping where the frame presses unevenly on the panel, usually as bright patches or streaks along an edge or in a corner. Its key trait: it stays in the same place and keeps the same shape whatever angle you look from.
IPS glow
IPS glow is a whitish or amber sheen in the corners caused by how IPS panels pass light at an angle. It is normal for the technology. It gets stronger as you move closer or off to the side and fades when you sit back and look straight on. If moving your head changes it, it is glow, not a defect.
Clouding and OLED
Clouding is uneven, blotchy brightness across the middle of the screen, common on VA and edge-lit LCD TVs. The near-black and dark grey steps show it best. OLED screens have no backlight, since every pixel makes its own light, so they cannot bleed or cloud. On OLED, check for burn-in instead.
When to return it, and the bezel screw trick
Some bleed on pure black in a dark room is normal for LCDs. Return a monitor if bleed is visible in normal content at your usual brightness, such as dark movie scenes, games or letterboxing, or if it is plainly worse than the panel the reviews showed. Swaps are a lottery, so decide inside the return window.
Bleed often comes from pressure. Loosening the screws on the back of the frame by a quarter turn, or gently massaging the bezel edge, can help. Go slowly, never force anything, and know that opening the case or damaging the panel may void your warranty. If it is still under warranty, a return is the safer fix.
Related tools
While the screen is on test, run the dead pixel test for stuck or dead pixels, use solid color screens to check uniformity in other colours, and try the burn-in test on OLED phones and TVs.
Frequently asked questions
What is backlight bleed?
Backlight bleed is light leaking through an LCD where the frame presses on the panel. It shows up as bright patches or streaks along an edge or in a corner, and it stays in the same place when you move your head.
How is IPS glow different from backlight bleed?
IPS glow is a whitish or amber sheen in the corners. It comes from how an IPS panel passes light at an angle, so it gets stronger as you move closer or off to the side and fades when you look straight on. Bleed keeps the same shape from every angle. Some glow is normal on IPS screens and is not a defect.
What is clouding?
Clouding is blotchy, uneven brightness, often across the middle of the screen. It is common on VA and edge-lit LCD TVs. The near-black and dark grey steps show it better than pure black.
How do I run the full-screen test?
Use a dark room, set the brightness you normally use, and turn off HDR and dynamic contrast. Start on pure black (#000000), then step through the shades with a click, the arrow keys, Space or a swipe. Look straight on first, then move your head. Press Esc or the X button to leave. If the controls fade, move the mouse or press G or Tab. On a touch screen, tap once to show them again.
Can an OLED screen have backlight bleed?
No. OLED pixels make their own light, so there is no backlight to leak and no clouding. To check an OLED phone or TV for image retention, use the burn-in test.
What are the four test colours?
Pure black is #000000, the main check for light leaking from the edges and corners. Near-black 4% is #0a0a0a and near-black 8% is #141414, which show clouding and uneven patches. Dark grey 13% is #202020, which shows tinted zones and the dirty screen effect. The page only draws these colours. It does not measure your screen.
When is backlight bleed bad enough to return a monitor?
A little bleed on pure black in a dark room is normal for LCDs. Return a monitor if the patches stay visible in normal content at your usual brightness, such as dark movie scenes, games or letterboxing, or if the panel is plainly worse than the one reviews showed. Trust your eyes rather than a long-exposure phone photo, and decide inside the return window.