Backlight Bleed Test & IPS Glow Checker
Fill your screen with pure black and check the edges and corners for light that shouldn't be there. The guide below explains how to tell backlight bleed, a hardware defect, apart from IPS glow, which is normal.
Click for fullscreen - dim your room first
Keyboard Shortcuts: F to enter fullscreen, G to toggle corner guides, Esc to exit.
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How to Use This Tool
What is this Test?
Backlight bleed is light escaping around the edges or corners of an LCD panel where the backlight should be fully blocked by the liquid crystal layer - it shows up as bright patches or streaks against a black screen, usually worst in dark rooms. IPS glow is a different, related phenomenon specific to IPS panels: a soft haze near the corners caused by the IPS layer itself, not a defect, that changes intensity as your viewing angle changes. This tool fills your screen with pure black so both are easy to spot; the guide below explains how to tell them apart.
Backlight Bleed vs. IPS Glow
- Backlight bleed: sharp, localized bright spots or streaks that stay in the same place and shape as you move your head - a hardware defect, present on any LCD panel type (IPS, VA, TN)
- IPS glow: a broader, softer haze concentrated in the corners that shifts in shape or intensity as your viewing angle changes - a known characteristic of IPS panels, not a defect
- The quickest test: sit directly in front of the screen, then slowly move your head side to side. Light that moves or changes with your angle is glow. Light that stays fixed in place and shape is bleed.
- Some bleed is normal on almost every LCD monitor to a small degree - the question is how much, and whether it is visible during normal (non-black-screen) use.:
How to Test Properly
- Dim the room - backlight bleed is far more visible in low ambient light, which is also when it is most likely to bother you in practice (movies, gaming at night):
- Let the display run for at least 15-20 minutes before judging - panels can show more bleed when cold, especially in colder rooms:
- Set brightness to a realistic level (30-50%), not maximum - bleed is easiest to see at low-to-mid brightness, but testing at 100% overstates how visible it will be in normal use:
- View from a normal, centered seating distance first, then check corners up close for anything the fullscreen view didn't reveal:
Testing Tips
- •Check all four corners and edges systematically, not just the one that first catches your eye
- •Photograph the screen from a fixed position if you plan to compare before/after a warranty exchange - phone cameras often exaggerate bleed, so use it for documentation, not diagnosis
- •Re-test after the panel has fully warmed up; a monitor tested cold, straight out of the box, will often look worse than it does after 20 minutes
- •Compare against a second, known-good display of the same model if you can - manufacturing variance means two units of the same monitor can differ
Keyboard Shortcuts
How this test works
The test shows pure black (#000000) in full screen, the darkest image an LCD can be asked to show, so any light you see is leaking from the backlight or glowing through the panel. The optional corner guides mark the four areas where bleed and glow usually appear, so you check them all the same way. Nothing is measured or sent; the judgement is your eye.
Pro Tip: A small amount of bleed in the corners, visible only on a black screen in a dark room, is normal on most LCD monitors and is not usually a warranty case. Bleed that is visible during regular content (dark movie scenes, game loading screens) in a normally lit room is a much stronger case for a return or exchange. Document it, and go through what to check before returning a monitor while you are at it.
Backlight Bleed vs. IPS Glow
Backlight Bleed
Light escaping around the panel edges where the backlight should be fully blocked. Shows up as sharp, localized bright patches or streaks - a hardware characteristic that varies unit to unit.
- • Stays fixed in place and shape as you move
- • Happens on any LCD panel type (IPS, VA, TN)
- • Some is normal; a lot, visible in real content, is a stronger case for return
IPS Glow
A soft haze near the corners caused by the IPS layer itself, most visible at an angle. It's a normal characteristic of IPS panels, not a defect - every IPS monitor has some degree of it.
- • Shifts in shape or intensity as your viewing angle changes
- • Specific to IPS (and IPS-type) panels
- • Not a warranty issue - it's how the panel technology works
The 10-Second Test
Start the test below in a dim room, then sit directly in front of your screen and slowly move your head side to side. Light that shifts or changes with your angle is IPS glow. Light that stays fixed in the same place and shape is backlight bleed.
Frequently Asked Questions
Is backlight bleed a defect I can return the monitor for?
A small amount visible only on a black screen in a dark room is normal on most LCD monitors and usually isn't covered by warranty. Bleed visible during regular content in a normally lit room is a much stronger case for a return, so check your retailer's return window.
Can backlight bleed be fixed?
Not reliably. It comes from how the panel and backlight were assembled. Some people loosen the screws on the back panel or the bezel with mixed results, but it is not a dependable fix and can void the warranty.
Does every IPS monitor have glow?
Yes, to some degree. IPS glow comes from how IPS panels are built, not from a manufacturing fault. The amount varies by panel and viewing angle, but it cannot be removed entirely.
Do VA and OLED monitors have backlight bleed?
VA panels can show bleed and some clouding, but much less glow than IPS. OLED screens have no backlight at all, so they cannot have backlight bleed or glow. Light on a black OLED screen means stuck pixels or panel damage.
Why does my monitor look worse straight out of the box?
Panels can show more bleed when they are cold. Let the display run for 15 to 20 minutes and test again at a realistic brightness of 30 to 50 percent, not at maximum.
How do I photograph backlight bleed for a warranty claim?
Darken the room, hold the phone steady at your normal viewing distance and lower the exposure until the photo looks like what you see. Phone cameras exaggerate bleed at default settings, so add a short description of how visible it is in normal use.
Written by R. Ottens, front-end developer & image editing specialist.