Find dead and sticky keys
Spilled coffee, a new mechanical keyboard or a second hand laptop: the fastest way to check a keyboard is to press every key once and see which ones never react. Keys are matched by their physical position, so the test works with US, UK, German, French, Turkish and every other layout. In Chrome and Edge the keys even show the letters of your own layout.
A key that stays lit after you let go is sticking. The panel shows the key name, the code and whether it was the left or right version, which helps when setting up shortcuts or games.
Ghosting and key rollover
Gamers need keys like W, A, Shift and Space to register together. Hold several keys at once and look at Most at once. Cheaper keyboards often stop at 2 or 3 keys in some combinations, which is called ghosting; gaming keyboards with n-key rollover register them all.