Check every key
Open the Keyboard Test and press each key in turn. Each one should light up once on the on-screen keyboard. A key that never lights is dead; one that lights twice or keeps going is chattering or stuck.
Dead or sticking keys
- Turn the keyboard upside down and tap it, or blow compressed air under the keys, to clear crumbs.
- For a sticky key after a spill, unplug the keyboard and clean under the keycap with isopropyl alcohol.
- On a mechanical keyboard, a key that registers twice (chatter) usually means a worn or dirty switch. Cleaning sometimes helps; otherwise the switch needs replacing.
- If a whole row or block is dead, the problem is in the keyboard's circuit, not the keys.
Ghosting and key rollover
Press several keys at once, such as W, A, Shift and Space for a game. Many cheaper keyboards register only two or three keys in some combinations and drop the rest; that is ghosting. "N-key rollover" keyboards register every key you hold. The Keyboard Test shows how many keys are registering at once.
If nothing works
Try another USB port or replace the batteries, and for a wireless keyboard, pair it again. If it works on another computer, the problem is with the first computer's driver or settings.
Once every key works, see how fast you type with the Typing Test.