White Level Test
Check how many near-white shades your monitor can show before highlights clip to pure white. Find the right contrast setting, spot a colour cast in one channel, and see whether your white looks blue or yellow. Free, runs in your browser.
White level checker
Use your normal brightness and picture mode, and turn off Night Light or blue-light filters. On the steps pattern, tap the highest number you can still tell apart from the white background. Full-screen mode gives the most honest result.
Tap the highest number you can still tell apart from the white.
Last visible step
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Tap a square on the steps pattern.
Per channel (R / G / B)
– / – / –
On the per-channel row, tap the last square you can see in each row.
White tint
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Open the tint check pattern and pick what you see.
Full screen: click, swipe or press the arrow keys or Space to change pattern, tap a square to mark it, Esc or the X button to exit. A browser sends 8-bit values only. The step chart is 230 to 254 on pure white (255, #ffffff), and the gradient runs from 224 to 255, one band per level. This page does not measure HDR peak brightness in nits.
How to read a white level test
Contrast sets the white level
On most monitors and TVs the contrast control sets how bright the top of the signal is drawn, while brightness sets the black level (check that with the black level test). Push contrast too high and the panel runs out of headroom: levels 245 to 254 all hit the same maximum, and the squares above disappear. Lower contrast until 250 to 252 are visible again, then stop. Going further only makes white look dull and grey.
Clipping and lost highlight detail
Clipped highlights cost you texture in clouds, snow, white shirts and bright skies, and they hide detail in photo editing. A good display shows steps up to 253 or 254; losing the last two or three is common and fine. If nothing above about 235 shows, suspect a range mismatch, where the PC sends full range and the display expects limited (16 to 235). The color range test checks that directly. If one row in the per-channel test fades earlier than the others, that channel clips first and bright areas pick up a tint.
Colour temperature and white tint
Web video, photos and games are mastered for a white point of 6500K (D65). Many monitors ship on a "cool" or "standard" preset closer to 7500K or 9300K because blue-white looks brighter in a shop. If white looks blue next to the neutral greys, choose 6500K, "warm" or "sRGB". It will look yellow for a day or two, then your eyes adapt. A yellow cast usually means a night mode or blue-light filter is on.
Why vivid modes clip, and test at your normal brightness
"Vivid", "dynamic" and many gaming presets raise contrast and saturation so the screen pops on a showroom floor, which is exactly what crushes the top steps into white. Does the "dynamic contrast" on the box mean more detail? Usually the opposite. Run the test in the mode and at the brightness you actually use, in your normal room lighting, because the result changes with both. Then confirm mid-tones with the monitor gamma test.
Related tools
- Black Level Test: the shadow side of this test, for setting brightness.
- Color Range Test: catch full versus limited range mismatches and banding.
- Monitor Gamma Test: check that mid-tones sit at gamma 2.2.
- Display Test: a full set of screen checks in one place.
Frequently asked questions
What is highlight clipping?
Highlight clipping is when the brightest parts of a picture are crushed into one white. On this chart, a step such as 250 or 254 should still look a little darker than the pure white background. If those steps vanish, clouds, snow, white shirts and bright skies lose texture.
Why do the near-white boxes disappear?
Each box is a real code value from 230 to 254, drawn on a pure white background (255, #ffffff). If contrast is too high, or a vivid or dynamic picture mode is on, the panel paints those values as the same white, so the boxes vanish. Lower contrast until 250 to 252 show again, then stop. Going further only turns white grey.
Does this page measure nits or a contrast ratio?
No. This is a visual check only. It cannot read brightness in nits, and it does not calculate a contrast ratio. You decide by eye which numbered step you can still separate from the white around it.
Which step should I still be able to see?
Tap the highest number you can tell apart from the white background. Seeing 253 or 254 means highlights are not clipped. Losing only the last two or three steps is common. If nothing above about 245 shows, lower contrast. If nothing from 230 up shows, check that the computer is not sending full range (0-255) to a display set to limited range (16-235) before you keep lowering contrast.
How do I leave the full-screen test?
Press Esc, or press the X button at the bottom of the screen. That button stays visible on a dark chip so you can see it on white. Arrow keys, Space, a click or a swipe change the pattern. Phones often have no Esc key, and some mobile browsers will not enter true full screen, so use the X button to close the test.
Why does one colour row fade before the others?
Each row lowers only red, only green or only blue, while the other two channels stay at 255. The number under a square is that channel value. If one row disappears at a lower number, that channel clips first and bright areas pick up a tint. Lower that channel gain, or lower contrast.
What if white looks blue or yellow?
The tint chart places neutral greys (64, 128, 192 and 230) on white so a cast is easier to see. A blue white usually means a cool preset, often well above 6500K. Choose 6500K, warm or sRGB, and turn off night light or a blue-light filter if white looks yellow. This is still a visual check, not a meter reading.