Keyboard tester
Check that every key works, see how many keys your keyboard can report at once, and confirm shortcut combos register before you blame yourself for a “broken” shortcut.
What the numbers mean
Tested counts keys that have lit up at least once. Max at once is your rollover in practice: press and hold as many keys as you can. If a three-key shortcut such as Ctrl + Shift + T never registers all three, your keyboard may be ghosting on that combination rather than the app ignoring you.
Keyboards read keys through a grid of wires. Cheaper boards share wires between keys, so certain combinations become ambiguous and the controller drops one. Boards with a diode per key (common on mechanical keyboards) avoid this and advertise “n-key rollover”.
Some keys never reach a web page: Fn is handled inside the keyboard, and the operating system may take Print Screen, the Windows key, or media keys first. Laptop layouts also vary, so a few keys above may simply not exist on yours.
Everything works? Put the keys to use: practise Windows shortcuts or Mac shortcuts.
Questions
How do I test my keyboard online?
Click inside the tester and press every key. Each key lights up on the on-screen keyboard as you press it and stays marked as tested, so any key that never lights up is not being received by the computer.
What is key rollover?
Rollover is how many keys a keyboard can report at the same time. Many office keyboards reliably handle only a few simultaneous keys; gaming and mechanical keyboards often support "n-key rollover", meaning every key at once.
What is keyboard ghosting?
Ghosting happens when certain key combinations are pressed together and the keyboard either drops a key or reports one you did not press, because of how the key matrix is wired. Hold the keys of a shortcut together in the tester to see if they all register.
Why do some keys not show up?
The Fn key is handled inside the keyboard and never reaches the browser. Keys such as Print Screen, the Windows key or media keys can be captured by the operating system first.