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Monitor Gradient and Banding Test

On a good monitor a gradient from black to white changes smoothly and you can see detail in both shadows and highlights. Open the full-screen test patterns and look for stripes of color or dark and bright steps that merge together.

Runs in your browser — nothing you enter is uploaded

Opens full screen. Click or press → to switch patterns, Esc to leave. Turn off night mode and eye-care filters first.

  • Gradients should change smoothly. Visible stripes (banding) mean the panel, cable or color settings show fewer than 256 levels.
  • Black level: count how many dark squares you can tell from the background. Seeing levels from about 5 up is good.
  • White level: count how many bright squares you can tell apart; about 250 and below should be visible.

Banding can also come from the operating system, graphics driver, browser or image compression, not only the monitor.

How to use

  1. Turn off night mode and eye-care filters and set brightness to your usual level.
  2. Click any pattern to go full screen. Click or press → for the next one and Esc to leave.
  3. Using the notes below, look for banding in the gradients and count the visible steps in the black and white level tests.

Options explained

Gradients
Drawn column by column from 0 to 255 rather than with a browser gradient, which may add dithering that hides banding.
Black and white level
Squares of levels 0–20 on black and 235–255 on white, each labelled with its level.

What the patterns show

An 8-bit channel has 256 levels, numbered 0 to 255. On a 1920-pixel-wide screen each level of the gradient is about 7.5 pixels wide, so in a clean 8-bit chain you should see no stripe wider than that.

The 32 gray steps pattern uses these levels from left to right:

0, 8, 16, 25, 33, 41, 49, 58, 66, 74, 82, 90, 99, 107, 115, 123,
132, 140, 148, 156, 165, 173, 181, 189, 197, 206, 214, 222, 230, 239, 247, 255

The black and white level patterns each show 21 squares in three rows of seven, in order of level. Black level covers 0 to 20 (0–6, 7–13, 14–20) and white level covers 235 to 255 (235–241, 242–248, 249–255). Squares that blend into the background tell you where shadow or highlight detail starts to be lost.

Frequently asked questions

Does banding mean my monitor is faulty?

Not necessarily. An 8-bit panel with limited-range HDMI output, color management or graphics driver settings can all cause it. Set the full RGB range in your graphics settings and turn off dynamic contrast, then look again.

I can't see the first black steps.

Raise brightness or "black equalizer", turn off dynamic contrast, and if your graphics card outputs limited RGB range, switch it to full.

Can I test a phone?

Yes. OLED screens usually have excellent black levels but may show tint or unevenness at low brightness.

Privacy

This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.

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