How do I test for dead pixels?

Go fullscreen and cycle white, black, red, green, and blue, checking the whole panel on each. Each field catches a different fault, so one colour on its own tests about a third of the problem.

Can I use this as a green screen for video calls?

On a second screen behind you, yes, and most conferencing apps will key it. Even lighting on the screen and enough distance to avoid green spill on hair and shoulders decide whether it looks good.

Does fullscreen work on iPhone?

iPhone Safari has no fullscreen API for web pages, so the colour fills the page and Safari bars remain. The colour field is identical either way. Android Chrome and desktop browsers go properly fullscreen.

Is it free, and is there a catch?

Free, no account, no upload. Traffic is counted with a cookieless analytics install and nothing about your screen leaves the browser.

What are the keyboard shortcuts?

F or Space to go fullscreen, Esc or a click to exit. On the cycling tests, Space and the arrow keys move between fields.

White screen

This page is the white screen. Go fullscreen to fill the whole display, or pick another colour. For cleaning, pixel checks, calibration, tracing, and chroma key.

F for fullscreen, Esc to exit

Colors

Each colour has its own page explaining what it is actually good for. Or use the picker above for anything else.

WhiteScreen cleaning BlackOLED test RedLighting effects GreenChroma key BlueVideo production YellowBright OrangeWarm lighting PinkAesthetic CyanCool tones PurpleCreative

Tools

Same fullscreen canvas underneath, each one aimed at a single fault, each with notes on what the result actually means.

White Screen Test Check a white field for dust, dead pixels, uniformity, and tint.
Dead Pixel Test Cycle white, black, red, green, and blue to find faulty pixels.
Stuck Pixel Fixer Rapidly flash colors over a stuck pixel to try to un-stick it.
Backlight Bleed Test Spot light leaking around the edges of an LCD panel on black.
Screen Burn-In Test Reveal retained images and uneven wear on OLED and plasma panels.
Monitor Test Full sweep: pixels, bleed, uniformity, and color channels.
Light Box Use the screen as a tracing panel or soft photography light.