Dead & stuck pixels
Nine pure colors, edge to edge. A dead pixel stays black, a stuck one stays lit.
1 minGuide
Color Banding Test
256-step ramps, drawn pixel-exact, to judge gradient handling. 100% in your browser - nothing is uploaded.
1 min5 patterns
Click the preview to run it full screen
Your display
Updates when you move the window to another screen- Resolution
- ---
- device px
- Pixel ratio
- ---
- devicePixelRatio
- Refresh rate
- ---
- measured in this browser
- Color gamut
- ---
- reported by the browser
- HDR
- ---
- standard range
- Orientation
- ---
- current
How to run the color banding test
01Turn off the filters
Night light, blue-light filters and any “dynamic contrast” or “black boost” mode off.
02Look at the grey ramp
From a normal distance, the steps should rise evenly from black to white.
03Check each color
Step through the red, green and blue ramps with the arrow keys or a swipe.
04Count the near-black steps
On the near-black ramp, count from the left how many steps you can tell apart.
What to look for
- Steps that look evenly spaced in brightness, with no sudden jumps.
- Groups of steps that merge into one wide band, or single steps that jump.
- A tint creeping into the grey ramp: pink, green or blue in the middle tones.
- On near-black: the first steps above 0 should still be distinguishable from pure black.
What counts as a defect
- Wide merged bands in the mid tones point to heavy processing or a poor color profile.
- If everything below about 16 merges into black, the graphics card may be sending limited range RGB over HDMI.
- Tint in the grey ramp that stays after resetting the monitor’s picture settings is a calibration issue.
What to do next
- Set the graphics driver output to full range RGB, then run the near-black ramp again. The black level squares in the gamma test confirm the fix.
- Reset the monitor’s picture mode to standard or sRGB and disable any color enhancement.
- Try without your ICC profile: an aggressive profile correction can introduce banding.
Other screen tests
Each one checks a different part of the panel. The guided check runs them all in order.
Uniformity & clouding
Flat greys and white show clouding, dirty-screen effect and tinted zones.
1 minGuide
Sharpness & geometry
One-pixel grids, checkerboards and circles expose scaling blur and bad geometry.
1 minGuide
Refresh rate & tearing
Measures the real frame rate in this browser and shows tearing on a moving bar.
30 sGuide
About the color banding test
A browser sends 8 bits per channel, so a ramp has 256 steps. This test draws each ramp as 256 equal-width steps, one exact value each, on the device pixel grid, so any unevenness you see comes from the display chain, not from the test. The near-black ramp zooms in on values 0 to 32, where most problems hide.
It is one of the tests in the Screen & Monitor Test, which also runs a guided check through every test and ends in an inspection reportfor a return or RMA. Every pattern is drawn on your screen's own pixel grid, 100% in your browser - no upload, no install, no account needed.
Frequently Asked Questions
No. Browsers compose the page at 8 bits per channel, so no web page can send more than 256 levels. The test shows how evenly your display chain reproduces those 256 levels, which is what you actually see day to day.
Common causes are limited range RGB (16 to 235) sent over HDMI to a monitor expecting full range, a black level setting that is too low, or a panel that crushes shadows. Switching the graphics driver to full range usually fixes the first one.
Every step is drawn with the same whole number of device pixels, so the steps are exactly equal. Most screens are not a multiple of 256 pixels wide (1920 / 256 = 7.5), so the width left over continues the first and last color to the screen edges instead of making some steps a pixel wider than others. The bracket under the ramp shows where its real steps begin and end.
Safari on iPhone does not allow web pages to go truly full screen. The test fills the whole visible area and hides all controls instead; rotate to landscape, or add the page to your Home Screen, to get the most of the panel in view. iPad and Android support real full screen.
No. Every pattern is drawn locally in your browser, and the inspection report is built and downloaded on your device. Nothing about your screen or your results leaves the browser, and no account is needed.
From the blog
monitor
Backlight Bleed vs. IPS Glow: How to Tell the Difference
Learn how to distinguish fixed backlight bleed from angle-dependent IPS glow, check a monitor in the right conditions, and decide what to document for a return or RMA.
Read →monitorMonitor Ghosting: How to Test Response Time and Overdrive
See what monitor ghosting and inverse ghosting look like, test motion in a browser, and use the results to tune overdrive without mistaking refresh rate for response time.
Read →monitorHow to Test a New or Used Monitor Before the Return Window Closes
A practical monitor inspection checklist for finding dead pixels, uneven backlighting, banding, ghosting, and other panel issues before you keep or buy a display.
Read →