Screen Colour Test
Gradients and solid fields, fullscreen, to expose banding, tint, backlight bleed and uneven brightness. Best judged in a dimly lit room with night-shift turned off.
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What each screen tells you
| Screen | Look for | What it means |
|---|---|---|
| Greyscale ramp | Visible steps | Banding — the panel is showing fewer shades than the image contains. |
| Red / green / blue ramps | Blotches, uneven fade | A weak channel. Blue bands most easily on almost every panel. |
| Hue sweep | Crushed or muddy hues | Oversaturation, or a narrow colour gamut. |
| White field | Tint, brighter edges | Colour temperature and uniformity. |
| Grey field | Patches, vignetting | The most revealing uniformity test there is. |
| Black field | Glow at the corners | Backlight bleed on LCD panels. |
Getting a fair reading
- Dim the room. Bright ambient light hides bleed and flattens gradients.
- Turn off night shift and any blue-light filter — they warm the screen deliberately and will make white look yellow.
- Sit straight on. Cheaper panels shift colour noticeably off-axis, which is a viewing-angle characteristic rather than a fault.
- Let the screen warm up for a few minutes. Brightness and colour drift slightly when a display is cold.
Banding is not always a fault
Many laptop and budget monitor panels are 6-bit and use dithering to approximate 8-bit colour. Mild banding on those is expected, not broken. What is worth investigating is heavy banding on a panel sold as 8-bit or better — that usually points at a display setting, a colour profile, or a cable negotiating a lower bit depth.
Other checks worth running
Uneven patches are a uniformity issue, but individual bad dots are something else — the dead pixel test covers those. If motion rather than colour is the problem, measure the panel with the refresh rate test.
More screen tools
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Online Ruler
A calibrated ruler in actual size — cm, mm, inches or pixels.
FPS Test New
Live frame rate, 1% lows and stutter, with a frame-time graph.
Refresh Rate Test New
Measure the true refresh rate of your display in Hz, live.
Dead Pixel Test New
Fullscreen solid colours that expose dead, stuck and hot pixels.
Aspect Ratio Calculator New
Work out and resize any aspect ratio, with a live to-scale preview.
Burn-in Test New
Check OLED and LCD panels for image retention, and try to clear it.
Touch Screen Test New
Find dead zones and check multi-touch by drawing on the screen.
Backlight Bleed Test New
Find light leaking around the edges of an LCD panel.
Ghosting Test New
Check motion blur, trailing and pixel response with moving objects.
Screen Size Comparison New
Put two displays side by side, drawn to true scale.
Frequently asked questions
How do I test my monitor colours?
Start the test and step through the gradients and solid fields fullscreen. Gradients reveal banding — visible steps where the fade should be smooth. Solid white and grey fields reveal tint and uniformity problems, where one part of the panel is brighter or a different shade from another.
What is colour banding?
Banding is when a smooth gradient shows as distinct stripes instead of a continuous fade. It usually means the panel is showing fewer colours than the image contains — a 6-bit panel simulating 8-bit, or a display setting clamping the range. Some banding is normal on cheaper panels; heavy banding on an expensive one suggests a settings problem.
Why does my white screen look yellow or blue?
That is the colour temperature. Most displays ship warmer or cooler than neutral, and night-shift style features deliberately warm the screen after dark. Turn those off before judging, then compare against a sheet of white paper in daylight.
What is backlight bleed?
Light escaping around the edges of an LCD panel, visible as brighter patches on a black screen — usually in the corners. Almost every LCD has some. It only matters if it is obvious during normal use in a dark room. OLED screens do not have it, because they have no backlight.
Can this test calibrate my monitor?
No, and no browser test can. Real calibration needs a hardware colorimeter that measures what the screen actually emits. This test shows you where the problems are; fixing them accurately needs the hardware.
What is the grey field for?
Uniformity. A flat mid-grey is the most revealing screen there is — the eye picks up brightness variation across it far more easily than on white or black. Patches, tinting or vignetting at the edges all show up here first.