Keyboard Tester

The Keyboard Tester shows a full on-screen keyboard layout that lights up as you press keys, making it easy to check that every key registers correctly and to spot ghosting or rollover problems — cases where pressing certain key combinations causes one or more keys to silently stop registering. It's the fastest way to test keyboard keys online: click into the keyboard area, then press keys as normal; each key turns green while held and stays lightly highlighted afterward, so you can see at a glance which keys you've tested and which still need checking. It doubles as a keyboard ghosting test and an n-key rollover test for gamers and mechanical-keyboard buyers.

It also tracks two numbers that matter for gaming and fast typing: how many keys are currently held down at once, and the maximum number of simultaneous keys detected during your session. This directly demonstrates n-key rollover (NKRO) limitations — many keyboards, especially older or cheaper ones, can only reliably detect 2 or 3 simultaneous key presses (a limitation called "ghosting") because of how their internal key matrix is wired, which matters a lot for games that require several keys held at once (movement plus jump plus a modifier, for example).

Beyond gaming, it's a practical diagnostic tool: after spilling something on a keyboard, dropping a laptop, or buying a used mechanical keyboard, pressing every key methodically and watching for ones that never light up (or don't stay lit while held) quickly reveals a stuck or dead key without needing to open a text editor and hunt for missing characters. It also shows the exact key name and code your browser receives for each press, which is useful when debugging a web app's own keyboard shortcut handling.

Every key press is processed entirely in your browser's JavaScript — nothing about what you type is transmitted anywhere, recorded, or stored beyond the current page session, and refreshing the page clears all highlighted keys.