Keyboard tester: keys, ghosting and rollover

• Click the keyboard picture so it has focus, then press each key once. Working keys turn green.
• A key that never lights up isn't reaching your PC: check for dirt under it, or try another USB port.
• A key that stays red after you let go is sticking. Press it a few times, or clean under the keycap.
• Click outside the picture to stop. Your browser keeps working as normal.

Hold the keys you use together in games, such as W + A + Shift + Space or W + D + Ctrl + E. Every key you hold should light up red at the same time. If one doesn't, your keyboard can't register that combination (ghosting), and you'll drop inputs mid-fight.

"Most keys at once" is your rollover. Gaming keyboards usually handle 6 keys or all of them (NKRO). Many laptop and office keyboards stop at 2 or 3 in some combinations.

Fn, media keys and some shortcuts (like the Windows key combos or Print Screen on some systems) are handled by your PC before the browser sees them, so they may not light up even when they work. Test them in their normal use instead. Fast tapper? Try the spacebar counter.