Screen & Keyboard Test

Screen & Keyboard Test checks the hardware you look at and type on. The display test fills your screen with pure colours one after another, so a dead pixel (always black) or a stuck one (always lit) stands out at once. Further screens show backlight bleed on black, uneven lighting on mid grey, banding in smooth gradients, how many near-black and near-white shades you can tell apart, and how sharp single-pixel detail and small text look.

It is ideal for checking a new monitor, laptop or phone while you can still return it, or a second-hand one before you pay. The keyboard tester shows a full US layout and lights each key as you press it, keeps every key that has worked in green, and reports the browser’s details for each press: key, code, keyCode, which side it is on and the modifier and lock states. A rollover counter shows how many keys the keyboard registers at once, which reveals ghosting. The mouse test checks all five buttons, the scroll wheel and double-clicks, and warns if a worn switch double-clicks by itself.

Everything runs in your browser. Nothing is recorded or sent anywhere, and there is nothing to install.

1. Clean the screen, set brightness high and press Start full test (or pick one test from the tiles).
2. Step through the screens with a click, tap, → or Space, and look closely at each one. Press Esc or × to stop.
3. For the Keyboard test, open its tab, click the test area and press every key. Tick “Highlight keys not pressed” to find any you missed.
4. For the Mouse test, click, scroll and press each button inside the box, including the side buttons.

• 14 full-screen test screens: 8 pure colours, 3 greys, gradients, black and white levels, sharpness
• Real full screen with the cursor hidden; tap, swipe, click or arrow keys to move between screens
• Pick-any-colour full-screen view
• Stuck pixel fixer with a clear epilepsy warning, consent tick box, size and time limit; never starts by itself
• Full ANSI keyboard with tested, held and not-yet-pressed keys, with or without the number pad
• Key, code, keyCode, location, repeat and modifier details for every press, plus an event log
• Rollover counter showing how many keys are held at once and the most so far
• Mouse test for left, middle, right, back and forward buttons, scrolling in four directions and double-clicks
• Double-click fault detector for worn mouse switches

• Dust and smudges look like dead pixels. Wipe the screen first, and if a dot moves when you wipe, it was dirt.
• Check backlight bleed in a dark room with brightness at maximum. Some glow at the edges is normal on LCD screens; bright patches visible in normal use are not.
• A stuck pixel shows a colour on the black screen; a dead pixel is black on the white screen. Only stuck pixels can sometimes be revived.
• Some key presses are taken by your system before the browser sees them (Fn, media keys, ⌘ Tab or Alt Tab). Those never light up here, and that does not mean they are broken.
• Laptop keyboards often register only two or three keys at once in certain combinations. That is normal, not a fault.