How to use the black screen test
- Dim the room lights and set your screen to the brightness you normally use.
- Press Pure black to fill the whole screen with black.
- Look slowly across the panel, corner to corner, for any dot that is lit or any bright patch along the edges.
- Lean a little to each side. A haze that moves with your head is glow, and a patch that stays put is bleed.
- Press Esc, then try Near black and compare how even the dark gray looks.
- Tap anywhere or press Esc to exit.
What a black screen shows
| What you see | Likely cause | What to do |
|---|---|---|
| A small bright dot in one spot | Stuck pixel | Note its color and position, then run the White Screen Test and Dead Pixel Test. |
| Bright patches along the edges that stay put | Backlight bleed | Compare against the maker's policy. Mild bleed is common on LCDs. |
| Soft haze in the corners that moves as you shift position | IPS glow | Normal for IPS panels. Lower the brightness or sit straighter. |
| Even dark gray over the whole panel | Normal LCD black level | Nothing is wrong. Lower the backlight in a dark room. |
| Blotches or dim areas on an OLED | Uneven aging or a display setting | Check the black level and power saving settings, then retest. |
| Faint vertical or horizontal lines | Panel or cable fault | Try another cable or port. Lines that stay point to the panel. |
Who this is for
- Buying a used monitor, TV or phoneCheck for bleed and bright dots on the spot, before you pay.
- Just unboxed a new displayDark scenes are where bleed shows up. Test it while the return window is open.
- OLED ownersConfirm that blacks are truly off and look for uneven patches that appear with age.
- Film and gaming fansSee how your screen handles dark scenes before blaming the video.
- Repair techniciansA quick first pass to separate backlight issues from pixel faults.
- Projector setupsJudge black level and light spill in the room you actually use.
Frequently asked questions
What is the difference between a black screen test and a white screen test?
They check opposite things. White drives every subpixel on, so it shows dead pixels and dirt. Black turns every subpixel off, so it shows light that should not be there: stuck bright pixels, backlight bleed, IPS glow and uneven black levels.
Why does my LCD look gray instead of black?
An LCD panel works by blocking a backlight, and no panel blocks all of it. In a dark room that leftover light shows as a dark gray. Lowering the brightness setting lowers the glow too. If one area is much brighter than the rest, that is backlight bleed.
What is the near black option for?
Pure black hides some faults. The near black fill is a very dark gray, about 5 percent brightness, that makes uneven shading, banding and black crush easier to judge. Switch between the two fills and compare how evenly the panel behaves.
Is a stuck bright pixel the same as a dead pixel?
No. A dead pixel stays black, so it disappears on a black screen. A stuck pixel stays lit in one color, so it stands out sharply against black. Run the White Screen Test as well, because the two tests find opposite faults.
My OLED screen is not completely black. Is it faulty?
Look closely first. A healthy OLED switches each pixel fully off, so a pure black fill should look like the screen is off. Faint blotches or a dim glow in one area can point to uneven panel aging, or to a display setting such as a low black level or a power saving mode.
What is IPS glow and is it a defect?
IPS glow is a soft, silvery or warm haze that shows in the corners of an IPS LCD on dark images, and it shifts as you move your head. It is a normal trait of the panel type. Bleed is different: it stays in fixed patches along the edges no matter where you sit.
Should I run this in a dark room?
Yes. Dim the lights, set brightness to your normal level and let your eyes adjust for a minute. Judge the screen from a normal viewing distance, then lean a little to each side to tell glow from bleed.
Why did the screen go fully dark and look like it turned off?
That is the test working. Pure black fills the whole display with #000000. Tap anywhere or press Esc to leave. On an OLED the panel really is emitting no light, which can look like it switched off.