Gray Screen Test
Show calibrated gray levels in fullscreen to observe panel uniformity, tint, and near-black behavior.
Test settings
Enter an integer from 0 to 255. Equal R, G, and B values create a digital neutral gray.
Enter an integer between 0 and 255.
Gray output and observation
Look for broad brightness variation, dirty-screen effect, vertical bands, or local shadows.
Record whether the screen or an area looks warm, cool, or otherwise tinted.
- Gray code
- 128
- Timer
- No limit
- Readiness
- 0/4
- Uniformity
- Not recorded
- Tint
- Not recorded
Equal RGB values define webpage output. Physical brightness, white point, and uniformity require visual or instrument checks.
Learn more
Test steps and keyboard controls
Choose a gray code, confirm native resolution, 100% zoom, and disabled enhancement, then enter fullscreen. Use up and down to adjust one level at a time, left and right for presets, H to hide controls, and F or Esc to exit.
Gray codes and #808080
When all three 8-bit channels use the same integer, the digital color is neutral gray. Code 128 is RGB(128,128,128) and #808080. It is the midpoint of the code range, not necessarily 50% physical luminance.
What different gray levels reveal
Check at least a dark, middle, and light gray so a conclusion does not depend on one level.
- Dark gray 32–64: near-black uniformity, vertical bands, residual images, and lifted black levels.
- Mid gray 96–160: broad dirty-screen effect, uniformity, and neutral tint.
- Light gray 192–224: brightness variation and differences in bright areas.
Scope and possible misreadings
Automatic brightness, HDR mapping, night mode, dynamic contrast, browser scaling, ambient light, and viewing angle affect observation. The page cannot measure nits, white point, Delta E, or a uniformity percentage.
Privacy, implementation, and sources
The tool runs locally and does not upload gray settings or observation records. Clipboard access is requested only when you choose to copy.
Native HTML, CSS, and JavaScript implementation without a third-party runtime library.
Frequently asked questions
How do I open a gray screen fullscreen?
Choose a gray code, confirm the conditions, and enter fullscreen. Use up and down to adjust the code and left and right to choose a preset.
What is a gray screen useful for?
Dark gray helps reveal near-black uniformity, dirty-screen effect, and residual images; mid gray shows broad uniformity and tint; light gray can reveal brightness variation. Check more than one level.
Why does gray look warm or cool?
White balance, picture mode, night mode, ambient light, viewing angle, and browser color management can all contribute. Equal RGB output is not guaranteed to look neutral on the panel.
What does gray code 128 mean?
It sets R, G, and B to 128, giving #808080. That is the digital midpoint, not 50% physical brightness or a fixed number of nits.