White for light and pixel checks, black for bleed, or any hex you type. Fullscreen instantly — nothing installed, nothing sent.
Keys: F fullscreen · ←→ switch color · 1–6 presets · Esc exit
A browser can't touch hardware brightness, so the light you get is capped by the slider you set in your OS. It also can't see your panel: this page paints the test conditions, and your eyes do the judging — our guided hunt tells you exactly what to look for. And on iPhone, Safari forbids true fullscreen for web pages; installing this site to the home screen removes the browser bars honestly instead of pretending they're not there.
No — a page can only ask every pixel for pure white. Hardware brightness lives with your OS: keyboard brightness keys on laptops, Control Center on iPhone, quick settings on Android. Max that out and white does the rest.
No page can; the browser has no camera pointed at your own panel. Flat color makes defects visible and the guided test says what to look for — a dark dot on white, a glowing dot on black. You do the looking.
Safari on iOS doesn't allow it for web pages, full stop. We fill the viewport instead, and if you want genuinely edge-to-edge color, add this site to your home screen — launched from there it runs without Safari's bars.
Browsers with the Wake Lock API (Chrome, Edge, Safari 16.4 and newer) let us hold the screen on, and the status line under the tool confirms when that's active. Elsewhere we say so plainly and your usual auto-dim schedule applies.
Nothing goes anywhere — there's no server behind this, no account, no ad script. The page caches itself on first visit so it opens offline afterward.
Copy the address — your color rides along in it (like ?c=00ff00). The share button does the copying for you.
Sometimes, not always. A stuck subpixel is glowing because its transistor didn't settle into the right state; forcing it through rapid color changes can jolt it loose. A dead (dark) pixel has no working transistor to jolt — no flashing anywhere will revive that. The fixer times the attempt honestly and never claims a guarantee.
Browsers don't expose that number directly, so we measure frame timing for a few seconds and estimate it — see display info. It's a solid estimate, not a spec-sheet reading, and it drifts low if the tab loses focus mid-measurement.
Yes, sort of — the dimmer lays translucent black over a base color, so the light reaching your eyes drops lower than the hardware floor allows. It's not a true off; it's the closest a browser gets.