Keyboard Tester
Press any key and watch it light up on an on-screen keyboard: check every switch, count simultaneous keys and spot dead or chattering keys.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
Spilled coffee on your keyboard, bought a second-hand mechanical board, or suspect one switch double-types or stopped registering? A keyboard tester answers those questions in seconds: press every key and watch the on-screen layout light up.
Keys that are currently held glow in one color; every key that has registered at least once stays marked in another. Walk across all rows, and any key that never changes color is a dead switch. The history line shows the exact key codes the browser received, which also helps identify keys that fire twice (chatter).
The simultaneous-keys counter tracks how many keys are registered at the same moment and keeps the maximum — a quick way to observe rollover and ghosting behavior on your board. Be aware that the browser and the operating system may cap how many simultaneous keys they report, so a low number is not always the keyboard's fault.
Everything happens locally through standard KeyboardEvent APIs: no keystroke leaves your device, no permissions are requested, and the tester works the same on Windows, macOS and Linux.
Example. Pressing the A key lights that key and appends its code to the press history, while a held key does not add extra counts because auto-repeat events are ignored.
Limit. The history line keeps only the latest 24 presses, and Tab, Space, quote, backtick, and F1 through F12 are swallowed so the page does not follow them.