Brightness Test
Step through labeled gray levels from black to white to set your screen brightness by eye.
Contrast Test
A contrast test shows whether your screen keeps the darkest and brightest shades apart from pure black and pure white. Every bar is labeled with its level from 0 to 255, so you can note where black crush or white clipping begins.
Showing Gray ramp · 1 of 4
All 16 steps should look distinct, from black on the left to white on the right.
Runs entirely in your browser. Test results, audio and video never leave your device.
How to check black level and white clipping
- Keep your usual picture settings and dim the room if you can: room light hides the darkest bars.
- Press Start test. Move through the patterns with Next and Previous, the arrow keys or a tap, and press Esc or Exit to leave. On a phone, turn it sideways if the bar numbers are hidden.
- On Gray ramp, check that all 16 bars look different, from 0 on the left to 255 on the right.
- On Near black, the first bar is 0, the same as the black surround. Note the lowest number you can tell apart from black.
- On Near white, the bars run from 255 on the left down to 231. Find the first bar from the left that you can tell apart from white. Any bars between it and 255 are clipped.
- On Checkerboard, look for black cells that turn gray or glow next to white ones.
What is black level?
Black level is how dark a screen’s black is and, as a setting, where its darkest shades start to separate from black. Set too high, black looks gray and the picture looks flat; set too low, the shades just above black sink into it, which is called black crush. A browser cannot measure black in nits, but numbered near-black steps show where your screen’s visible range begins.
What causes black crush and white clipping?
Note the numbers where bars disappear, then find the row that matches.
| What you see | Likely cause | What to try |
|---|---|---|
| The lowest few Near black bars merge with black | Black crush: brightness set too low for the room, or a dark gamma setting | Raise brightness a step at a time, then check midtones with the Gamma Test |
| The first Near white bars after 255 merge with white | White clipping, also called white saturation: contrast set too high, or a vivid picture mode | Lower contrast, or switch to a standard or sRGB picture mode |
| Every bar up to 16 looks black and every bar from 235 up looks white | A full-range signal on a display set to limited range | Match the range settings, as described below |
| Black looks dark gray even in a dim room, and every near-black bar is easy to see | A limited-range signal on a display set to full range, or brightness set too high | Match the range settings, or lower brightness |
| Neighboring Gray ramp bars look the same | Dynamic contrast or other picture processing, or an extreme setting | Turn off dynamic contrast and reset the picture mode |
| Black looks gray only near the edges or corners | Backlight bleed, not black level | Check it with the Backlight Bleed Test |
What is full vs limited RGB range?
Full range uses all 256 levels, 0 to 255, from black to white, and is the usual choice for computers. Limited range, used for video and TV, puts black at 16 and white at 235. The graphics card and the display have to agree on which one is in use. A mismatch is most common over HDMI.
To fix it, set both ends to the same range: the output range in your graphics driver (NVIDIA calls it Output dynamic range) and the display’s input range option, often named HDMI black level, RGB range or black level. Then check Near black and Near white again.
What this test can detect
- Black crush: near-black bars that vanish into the black surround.
- White clipping, or white saturation: near-white bars that merge into white.
- The sign of a full vs limited range mismatch: every bar up to 16 black and every bar from 235 up white.
- Neighboring steps on the 16-step gray ramp that look the same.
- Black cells that look gray or haloed next to white ones on the checkerboard.
How it works
The page draws each bar as a plain block of gray, not an image, so nothing is scaled or compressed. Gray ramp shows 16 levels 17 apart, from 0 to 255. Near black shows 0 to 16 in steps of 2, then 20 and 24, on a black surround; Near white shows 255 down to 239 in steps of 2, then 235 and 231, on white. Each bar is labeled with its level. Checkerboard is 16 by 8 black and white cells sized to your screen.
The page reads nothing from your screen: you judge which levels your display keeps apart.
Limitations
- The finest step is 2 of 255 levels, so it cannot show whether single-level steps right above black are visible.
- It shows symptoms, not causes: the same crushed bars can come from the panel, the graphics driver’s output range, color management or room light.
- The bars are gray, so crush or clipping in just one color channel shows only as a faint tint, if at all.
- On a screen with local dimming, such as a mini-LED monitor, the backlight behind the white cells on Checkerboard can also light the black cells next to them. Halos there are likely blooming, not a black level problem; the Blooming Test checks them.
Frequently asked questions
Does this test show my monitor’s contrast ratio?
No. Contrast ratio is the luminance of white divided by the luminance of black, and both take a light meter or colorimeter to read. The bars show which levels your screen keeps apart, which is a different thing from the ratio on a spec sheet.
How many near-black bars should I be able to see?
Ideally all of them from 2 up, in a dim room. The first one or two often blend into black on an LCD or in a lit room, which is normal. If most bars below 16 vanish, check brightness and the range settings.
Is black level the same as brightness?
No, though the names overlap. On many TVs the control named Brightness sets the black level, while a separate backlight or light setting controls how bright the screen gets. On most LCD monitors, Brightness sets the backlight, which lifts black along with everything else. The Brightness Test helps you choose that overall setting.
Why do near-black shades disappear on my OLED?
Some OLED panels struggle to light pixels very faintly, so the lowest steps merge into black even though black itself is fully dark. A dark picture mode or a high gamma setting adds to it. Compare Near black across picture modes in a dim room before judging the panel.