Display utility · runs entirely on your device
A perfectly black screen,
one press away.
Black out a monitor, hunt for dead pixels, check backlight bleed, or see what your refresh rate really looks like. No sign-up, no tracking, works offline.
Calibration patterns
Six quick checks for any panel.
Each opens full screen, drawn pixel-for-pixel at your display's native resolution. Use ← → to move between them.
Motion lab
See your refresh rate, not just the number.
Follow the moving objects with your eyes. Smooth, sharp motion means your display and browser are keeping up; smearing or doubled edges show persistence, ghosting or dropped frames.
- Refresh
- —Hz
- Frame time
- —ms
- Step
- —px / frame
- Dropped
- 0frames
Your display
What this browser reports.
Read live from your device. Nothing here is sent anywhere.
- Resolution
- — physical pixels
- Refresh rate
- measuring… as delivered to the browser
- Pixel ratio
- — device px per CSS px
- Viewport
- — CSS pixels
- Colour gamut
- — —
- HDR
- — dynamic range
Field guide
What to look for.
Dead and stuck pixels
On black, a stuck pixel shows as a tiny dot of red, green, blue or white that never switches off. On white and the primary colours, a dead pixel shows as a dark speck. Step through the colours with the arrow keys and scan the panel slowly from about arm's length.
Backlight bleed and glow
Open the black screen in a dark room at normal brightness. Cloudy light patches along the edges are backlight bleed; a haze that shifts as you move your head is IPS glow. OLED panels should look like the screen is switched off.
Does a black screen save power?
On OLED and AMOLED panels, yes: black pixels are physically off. On LCD panels the backlight stays on, so the saving is small, but the room still gets much darker.
Why the motion lab reports a lower rate than my monitor
The lab measures what the browser actually delivers. Battery-saver modes, a 60 Hz setting in the operating system, mixed-refresh multi-monitor setups and some browsers' frame caps all lower it. If the number is below what you paid for, check the display settings first.
Full screen on iPhone
iPhone browsers don't allow pages to go truly full screen. Use Share → Add to Home Screen and open Black Display from the icon: it then runs edge to edge with no browser bars, and keeps working offline.