How the test works
The test shows three dark levels, one at a time, full screen: pure black, a 5% grey and a 15% grey. Unlike the dead pixel test it never advances on its own. Your eyes need about thirty seconds in the dark before they can see faint light, and a level nobody has adapted to has not been checked. The caption in the corner counts down those thirty seconds once, then reminds you to compare the corners with the centre. A tap or the right arrow moves to the next level; Escape, a swipe down or the cross leaves.
Each level has a purpose. On pure black an LCD blocks the backlight as well as it can, so any light you see near the edges is escaping around the frame: that is bleed. IPS glow also appears on black, but it moves with your viewing angle. The two greys light every pixel a little, which reveals clouding and uneven zones in the diffuser that black hides, and they are the only levels that mean anything on an OLED, where black is simply off.
- Wait for real darkness: curtains closed, lamps off, phone face down.
- Set the system brightness to 100% for the first pass, then to your usual level.
- Sit straight on at normal viewing distance and only then judge the corners.
Nothing is measured or sent. The page draws a shade of grey; the observation is yours.
What the result means
The result card counts the levels you looked at and how long the test ran. The observation is the result:
- An even field on all three levels. No meaningful bleed. Edge-lit panels this clean exist, but they are not the majority, so keep this one.
- Light in a corner or along an edge on black that does not move. Backlight bleed. Judge it at your normal brightness; if it disappears there, it is cosmetic.
- A sheen that shifts when you move your head. IPS glow, inherent to the panel type. Not a defect and not a reason for a claim.
- Brighter or darker patches in the middle of the greys. Clouding, or "dirty screen effect". Most visible on the 15% grey and on panning shots in sport and games.
- One side clearly darker than the other on grey. Uneven backlight. It is worth comparing with another unit of the same model before deciding.
What to do about a problem
Bleed is mechanical, so mechanical remedies are the ones that work. On a monitor, slightly loosen the screws at the back of the frame; the bezel presses on the panel and creates the leak. A new panel often settles over two to four weeks of normal use. A gentle circular massage of the bleeding corner with a soft cloth, screen off, reduces it on some units and does nothing on others; do not press hard on a laptop. Clouding does not respond to any of this; it is inside the diffuser.
Lowering brightness reduces the visibility of everything on this page, because the backlight is what leaks. If your bleed only exists at 100% and you run the screen at 30%, it exists only on the test page.
When to return or claim the warranty
Bleed is the classic case for the return window rather than the warranty: most manufacturers treat a moderate amount as normal and reject claims, while a shop will exchange a unit within fourteen days without discussion. If you do file a claim, photograph the screen in a dark room with a locked exposure and a reference object in the frame, because an unlocked phone camera turns a faint glow into a bright one and the claim will be dismissed. Include which level showed the problem and at what brightness. A second exchange rarely brings a better panel of the same model; if the second unit bleeds too, consider a different model.
Frequently asked questions
How do I tell backlight bleed from IPS glow?
Move your head. Glow is a sheen that changes and fades as your viewing angle changes and is weakest when you look straight on. Bleed stays in the same spot however you look at it, usually along an edge or in a corner, because light is physically escaping around the panel's frame.
Why three levels instead of just black?
Pure black shows bleed and glow on an LCD but hides everything on an OLED, where black pixels are off. The 5% and 15% greys drive every pixel a little, so clouding, dark corners and uneven zones appear on both panel types. Each level answers a different question.
How much bleed is normal?
Almost every edge-lit LCD has some. It counts as acceptable when it is invisible on real dark content at the brightness you use, and only shows up on a test page at maximum brightness in a dark room. A corner that glows over a film's letterbox bars in a dim living room is not acceptable.
Can backlight bleed be fixed?
Sometimes. Bleed comes from pressure of the frame on the panel, so loosening the rear screws slightly or letting a new monitor settle for a few weeks can reduce it. Gently massaging the bleeding corner with a microfibre cloth helps on some units. If none of that works, the panel needs to be replaced.
Do I need this test on a phone?
Only if the phone has an LCD. OLED phones cannot bleed, because there is no backlight. LCD phones, tablets and cheaper laptops are the devices where bleed is most common and most visible, especially on dark photos and when reading at night.