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Backlight bleed test: check your screen for light leaks
A free backlight bleed test. It shows a pure black screen, a near-black screen and a blooming test, so you can see light leaking at the edges, cloudy patches and halos around bright objects. Use it in a dim room with brightness turned up.
- Dim the room and turn screen brightness all the way up.
- Sit straight in front of the screen, at your normal distance.
- Click Start, then step through the screens with a click or the Space bar.
- On the blooming screen, move the pointer around. The white dot follows it.
Finished. A soft glow at the edges is normal for most LCD screens. Bright blotches inside the screen are a different thing, usually pressure marks. Here's how to tell.
What each screen shows
| Screen | Look for |
|---|---|
| Black | Light leaking at the edges and corners. That's bleed. |
| Near black | Cloudy or uneven patches across the screen, sometimes called clouding. |
| Blooming | A halo around the white dot. Normal on mini-LED screens, minimal on LCDs. |
| Grey | Bright or dark blotches. Those are usually pressure marks, not bleed. |
What your results mean
- A faint glow at the edges. Normal on most LCD screens, including MacBook Airs. Nothing to fix.
- A halo around the dot on a MacBook Pro. Normal blooming on mini-LED screens.
- Bright patches or keyboard-shaped marks inside the screen. Pressure damage. Here's how pressure marks differ from bleed.
- A dark or dead band along one edge. That's not bleed. The panel is damaged there. See one side of the screen black.
Questions
How do I check for backlight bleed?
In a dim room, turn brightness to maximum and show a completely black screen. Light leaking from the edges or corners is backlight bleed. Look straight at the screen, because viewing it from an angle adds a glow that isn't bleed.
Is backlight bleed normal on a MacBook?
A faint glow at the edges is normal on LCD MacBooks, the MacBook Air and older MacBook Pro models. MacBook Pros with mini-LED screens show a halo around bright objects on black instead, called blooming, which is also normal. Strong patches that are visible in normal use are worth showing to Apple under warranty.
Does backlight bleed get worse over time?
Normal bleed usually stays the same. Bleed that appears suddenly or spreads, especially after the MacBook was dropped or pressed, is more likely pressure damage.
Why does backlight bleed look worse in photos?
Phone cameras raise exposure on dark scenes, which makes a faint glow look much brighter than it is. Judge it with your eyes, not a photo.
A dark band instead of a glow?
Bleed is light leaking in. A band along one edge that stays dark on every colour is damage, and the rest of the screen still works. CrackMac blacks out that strip and keeps your work on the part that works.
- Works on macOS 13 or later, Apple silicon and Intel.
- Free for 30 minutes of use, then a one-time price. No subscription.
- A refund within 7 days, no questions asked.