Black Level Test
Check how dark your screen's blacks stay and whether shadow detail survives. Near-black steps, a 0 to 32 gradient and PLUGE bars show black crush, raised blacks and HDMI range mismatches, so you can set brightness correctly. Free, runs in your browser.
Black level checker
Dim the room, look straight on, and give your eyes a few seconds to adjust. Find the lowest numbered square that separates from the black background. Full screen is the fairer look, because the bright page around this preview makes black look darker than it is. Then tap that square here to record it.
Find the first numbered square you can tell apart from black.
Tap the first visible square above, or pick an option:
Full screen: swipe, arrow keys or Space change the pattern. On the steps, note the lowest square that separates from the background, then tap it here. Esc or the X exits, and the bottom bar stays visible. Values are 8-bit sRGB levels sent by the browser; night modes, HDR, colour filters and auto-brightness all change what you see, so turn them off first.
Set brightness in five steps
- Turn off auto-brightness, HDR, dynamic contrast and night light, and dim the room lights.
- Open the near-black steps in full screen and turn the monitor or TV brightness setting all the way down.
- Raise brightness one notch at a time until square 2 or 3 just appears and square 1 is barely there.
- Check the pure black screen: it should still look black, not grey. If it turns grey before step 3 appears, back off one notch.
- If no brightness setting gives both a black background and a visible step 3, fix the HDMI range (below) and repeat. Then check highlights with the white level test.
How black level works
Brightness moves black, not white
On most monitors and TVs the control labelled brightness sets the black level, and contrast (or backlight on some TVs) sets the white level. Too low and the darkest shades merge into black, called black crush, so you miss enemies in dark game corners and detail in night scenes. Too high and black turns into a milky grey. The goal is the lowest setting where step 2 or 3 is still visible.
HDMI limited vs full range
Video uses limited range, where black is 16 and white is 235. PCs use full range, 0 to 255. If the PC sends full range to a screen expecting limited, everything from 0 to 16 is clipped to black, and this test shows nothing until about step 16. If the PC sends limited to a screen expecting full, black arrives as dark grey and the picture looks washed out. Set the GPU output (for example "Output dynamic range" or "RGB Full/Limited" in the graphics driver) and the screen's "HDMI black level" to the same thing. The PLUGE bars show this too: from a PC, the 8 and 12 bars should look darker than the background.
OLED vs LCD and IPS glow
An OLED switches pixels off for true black, so it often shows step 1 against a perfectly black background, though some OLEDs crush the first few steps near black. An LCD always leaks some backlight, so its black is dark grey in a dim room and IPS panels add a silvery glow at an angle. That glow is not raised blacks from a settings error. Check edges and corners with the screen bleeding test.
Getting a fair reading
Room light reflects off the panel and hides near-black steps, so a dim room gives the truest result. Look straight on, as viewing angle shifts dark tones on IPS and VA panels. If step 4 to 7 is your first visible square even after tuning, the panel's gamma may be too dark in the shadows; the monitor gamma test will show it. Reviews quoting a huge contrast ratio mean little if the first ten shades are crushed.
Related tools
- White Level Test: check highlight clipping and set contrast.
- Monitor Gamma Test: see if mid-tones match the 2.2 standard.
- Screen Bleeding Test: find backlight bleed and IPS glow.
- Display Test: a full set of screen checks in one place.
Frequently asked questions
What is black crush?
Black crush is when the darkest shades merge into the background, so shadow detail in games and night scenes disappears. On the near-black steps, the low numbers look the same as the black around them. Raise the brightness setting, which on most screens moves black rather than white, until square 2 or 3 just separates from the background.
How do OLED and LCD black levels differ?
An OLED can switch pixels off, so the background can be truly black and square 1 may still show. Some OLEDs still crush the first few steps. An LCD always leaks some backlight, so black looks dark grey in a dim room, and an IPS panel adds a silvery glow when you look from an angle. That glow is the panel, not a brightness setting.
How do I leave full screen?
Press Esc, or use the X on the light bar at the bottom. That bar stays on screen, so you can always tap it. Arrow keys, Space, a swipe or a click on an empty area change the pattern. If the browser will not enter full screen, the same overlay still covers the page and the X closes it.
Does this measure nits or a black-level percentage?
No. This is a visual check, not a meter. The page draws known 8-bit levels and you judge which step separates from the background. It cannot read the panel, the room or a brightness in nits, and it does not calculate a percentage.
Which step should I look for?
Dim the room, sit straight on and give your eyes a few seconds. On the near-black steps, tap the lowest number you can just tell apart from the black background. Square 2 or 3 just visible, with the background still black, is a good target. If the first square you can see is much higher, blacks are crushed.
What do the PLUGE bars mean?
The background and the middle bar are level 16. Bars 8 and 12 are darker, and bars 20 and 24 are lighter. On a PC set to full range, 8 and 12 should look darker than the background. If they vanish, black is clipped, often because the PC sends full range (0 to 255) while the screen expects limited range (16 to 235). Set both ends the same.