Tools/Screen Tests

Color Range Test

Check your monitor for colour banding with full-screen grey, RGB and CMY gradients, a dark-grey banding finder, a hue sweep and a saturation ladder. Bands can come from the browser, the OS or the panel. Free, runs in your browser.

Gradient and banding test

Pick a pattern, then go full screen and view it from your normal seat. Click, tap, swipe or press the arrow keys or Space to change pattern. Esc or the X button exits. Turn off night light and blue light filters first, as they add banding of their own.

All ramps 1/12

Grey, R, G, B, C, M, Y from black to full. Each bar should fade evenly with no wide bands or colour tints.

Patterns

10-bit attempt. Draws smooth ramps on a Display P3 canvas and asks for a 16-bit float buffer when the browser allows it. A normal canvas gradient is still 8-bit, and bands can come from the browser, the OS or the panel. This does not measure bit depth or prove a 10-bit panel.

Gamut reported: ...
HDR active: ...
screen.colorDepth: ...
Canvas: ...

These are what the browser reports, not measurements. screen.colorDepth says 24 on most 10-bit setups too. In standard mode the ramps are exact 8-bit columns with no dithering. The hue sweep is a browser gradient, which is 8-bit on a normal canvas.

Keys in full screen: → ↓ Space Enter next, ← ↑ back, Esc or the X button exits. The X stays on screen. On phones that block the Fullscreen API (iPhone Safari), the test fills the browser window instead.

How to read a banding test

What banding is and where it comes from

Banding is a smooth gradient breaking into visible stripes. An 8-bit channel has 256 levels, so a full black to white ramp on a 2560 pixel wide screen is already made of 10 pixel steps; that is normal and usually invisible. Bands become obvious when levels are lost on the way: the browser (a normal canvas gradient is 8-bit), the operating system (a colour profile or night light), video and image compression, a 6-bit panel without good dithering, or a dynamic contrast mode that stretches the image. Wide bands of uneven width, or a green or magenta tint in grey, point to that kind of processing.

Read the result honestly

On the banding finder you should see 65 steps of even width. That is the test working, not a fault. Look instead for steps that are wider than their neighbours (levels merged), steps that change tint, or the left side collapsing into one black block, which hints at crushed blacks or a 0 to 255 versus 16 to 235 mismatch. A smooth gradient on this page is 8-bit in a normal browser canvas. Bands can come from the browser, the operating system, or the panel. This page cannot measure bit depth, and it cannot prove an 8-bit or 10-bit panel.

"1.07 billion colours" on the box

Many monitors sold as 10-bit or "1.07 billion colours" are 8-bit panels using FRC, which flickers between two neighbouring levels to fake the one in between. That is fine for almost everyone, and a good 8-bit plus FRC panel looks identical to native 10-bit in real use. The spec only matters when software, cable and GPU actually send 10-bit, which mostly means HDR video and pro photo or video apps.

Settings that change the result

Check the colour profile (ICC) first: a calibration profile applied on an 8-bit pipeline throws levels away and is a common cause of banding. NVIDIA, AMD and Apple GPUs dither their output to hide this, and some drivers let you turn that on or off. HDR mode on Windows often makes SDR gradients worse. Finally, make sure the GPU output and monitor agree on full range (0 to 255) or 16 to 235; a mismatch shows as grey blacks or crushed shadows, which the black level test makes easy to spot.

Related tools

White Level Test: check that near-white shades are not clipped.
Black Level Test: find crushed or raised blacks and range mismatches.
Monitor Gamma Test: see if mid-tones are too dark or too bright.
Display Test: a full set of screen checks in one place.

FAQ

Frequently asked questions

What does this banding test show?

It draws grey, red, green, blue and other ramps so you can look for stripes in a fade. Banding is a gradient breaking into those stripes. The page does not measure bit depth.

Can this tell if my monitor is 10-bit?

No. A normal browser canvas is 8-bit, and a smooth gradient is 8-bit too. The 10-bit attempt asks for a Display P3 canvas and a 16-bit float buffer, but the browser, the operating system and the panel may still show 8 bits. Bands, or a lack of bands, do not prove an 8-bit or 10-bit panel.

Why do I see bands?

Bands can come from the browser, the operating system or the panel. A colour profile, night light, a 6-bit panel or a mismatch between 0 to 255 and 16 to 235 can also drop levels. Turn those filters off and view the pattern from your normal seat.

How do I leave the full-screen test?

Press Esc or the X button. The X stays on screen. Arrow keys, Space, a click or a swipe change the pattern. iPhone Safari often blocks real full screen, so the test fills the browser window and you leave with the X button.

What should the banding finder look like?

Grey levels 0 to 64, as 65 steps of even width from left to right. Even steps are normal. Look for steps that are wider than their neighbours, a tint, or the left side crushed into one black block.

Which way do the ramps run?

Grey, red, green, blue, cyan, magenta and yellow each run from black on the left to full colour on the right. On All ramps, that order is top to bottom. The hue sweep runs every hue left to right, with white at the top and black at the bottom.

What do gamut, HDR and screen.colorDepth mean here?

They are browser reports, not a measurement. screen.colorDepth is often 24 even when a panel can do more. The canvas line shows the drawing buffer the browser gave this page. None of these values measure bit depth.