Monitor Black Level Test.
Fill your screen with pure black and a ladder of near-black shadows to see how deep your blacks go, whether the darkest steps stay distinct, and to catch black crush or raised, greyish blacks — free, in your browser.
How the black level test works
“Black” on a screen is never truly zero light on an LCD — the backlight leaks through the panel even when a pixel is told to be black. How much it leaks is the black level, and it decides how deep and contrasty the whole image looks. This test floods the screen with pure black, then walks up a ladder of near-black shadow values so you can judge two things by eye: how dark your black really is, and whether the darkest shadow steps stay separable.
- 1. Kill the lights. Do this in a dark room and let your eyes adjust — ambient light hides raised blacks and low shadow detail completely.
- 2. Start on pure black. Look for an even, inky field. A grey cast, or brighter clouds and corners, means raised blacks or backlight bleed.
- 3. Step up the shadows. Move through RGB 1, 2, 3 … Each step should look a hair lighter than the last. If the first several are all identical to black, the panel is crushing shadow detail.
- 4. Run the sweep. The 0→20 shadow sweep shows the same thing as a smooth gradient — the point where it lifts out of black is your panel's shadow floor.
Black level by panel type
Black level is set by the panel technology. OLED turns pixels fully off, so it wins outright; among LCDs, VA is far deeper than IPS or TN. These are typical ballpark figures — treat them as “what good looks like,” not a measurement of your specific screen.
| Panel | Typical black level | Native contrast |
|---|---|---|
| TN | 0.5 – 1.0 nits | ~600 : 1 – 1000 : 1 |
| IPS | 0.3 – 0.5 nits | ~1000 : 1 – 1500 : 1 |
| VA | 0.03 – 0.08 nits | ~3000 : 1 – 5000 : 1 |
| OLED | ≈ 0 nits | effectively infinite |
Because a browser can only send colour values and never measure the light your panel emits, this test is a by-eye check for raised blacks, black crush and uneven backlighting — not a substitute for a colorimeter when you need real nits.
What your results mean
Match what you see on the shadow ladder to what it means for your panel.
| What you see | What it means | What to do |
|---|---|---|
| Pure black looks even and inky, and each near-black step (RGB 1–16) is a hair lighter than the last | Deep black level with no crush — a good panel, especially VA or OLED | Nothing to do. |
| Pure black looks grey rather than inky, even in a dark room | Raised black level — typical of TN/IPS panels with lower native contrast | Check the panel-type table above; a VA or OLED panel goes deeper if this matters to you. |
| The first several near-black steps (RGB 1–4) look identical to pure black | Black crush — the panel can't resolve the darkest shadow detail | Re-test in a fully dark room first; if it persists, it's a panel limit. |
| Brighter patches or a corner glow on the black field | Backlight bleed or IPS glow, not black level itself | Run the uniformity test to tell bleed from glow. |
| Steps that were distinct in the dark merge together under room light | Ambient light washing out shadow detail — not a panel fault | Re-test with the room fully dark and your eyes adjusted for a minute. |
Frequently asked questions
What is a monitor’s black level?
Black level is how much light your screen still emits when it is showing pure black. Lower is better: a true black looks inky, while a raised black level looks dark grey. Black level, together with peak white, sets a panel’s contrast ratio — the single biggest factor in how “deep” and punchy an image looks.
How do I run the black level test properly?
Do it in a dark room and let your eyes adjust for a minute — raised blacks and shadow detail are invisible under bright light. Go full screen on pure black first, then step through the near-black fields (RGB 1, 2, 3 …). On a good display each step looks very slightly lighter than the one before; if the first several steps are indistinguishable from pure black, your panel is crushing shadow detail.
Why do some near-black steps look identical to pure black?
Two reasons. Either the panel genuinely can’t resolve those levels (black crush — dark detail is lost), or the surrounding light is washing them out. Test in the dark first. Note that a browser sends 8-bit values, so RGB 1 is the smallest step above black it can request; if you can’t see it, that’s your panel or your room, not the test.
What black level counts as good?
It depends on the panel technology. OLED switches pixels fully off, so black is essentially perfect (infinite contrast). VA panels are the best LCDs for blacks (deep, ~3000–5000:1 contrast). IPS and TN have visibly raised blacks and lower contrast, which shows as “IPS glow” or a greyish look in the dark. See the reference table on this page.
Can this measure my black level in nits?
No — a web page can only send colour values, it can’t read the light your panel emits. Measuring actual nits needs a colorimeter or luminance meter. Use this test to compare shadow steps by eye and catch crushing or raised blacks; use hardware if you need real numbers.