Keyboard Tester

How to use

1. Click the keyboard diagram or focus it with Tab, then press a key — it lights up on the 104-key diagram below.
2. Hold several keys together to see how many register at once (NKRO/rollover).
3. Switch Layout to Korean to check the 2-set jamo printed on a Korean keyboard.
4. Watch for a red warning if a key double-fires (chatters) or stays stuck.
5. Select Reset to clear the session and test a different keyboard.

What rollover (NKRO) actually means

Rollover is the number of keys a keyboard reports at the same time. Some keyboard matrices block particular combinations; true ghosting is different, because it reports a key you did not press. Full N-key rollover (NKRO) means every key can be reported independently. This page records the largest combination the browser received, so a result of 10 proves at least 10-key rollover — it does not by itself prove full NKRO. Try combinations that matter to you, such as Shift+Ctrl+W+A+S+D, and watch whether every intended key lights up.

Why some keys never make it to the browser

Browsers and operating systems intercept certain keys before a web page ever sees them. Cmd+Tab, Alt+Tab, F11 fullscreen, browser-tab shortcuts and some media keys are handled at the OS or browser level, so they may not register here even on a fully working keyboard. That is a known limit of any browser-based keyboard tester, not a sign your key is broken — if a letter, number or punctuation key stays grey here, that is the more reliable signal of a real hardware problem.

Stuck keys and chattering switches

A key that stays highlighted long after you lift your finger can point to a stuck switch or debris under the keycap; this page flags any key still reported as held after 5 seconds. A key that registers twice from one tap can be switch chatter. This tester marks a quick press-release-press sequence within 60 milliseconds as a clue, not a hardware diagnosis — test the key several times before cleaning or replacing a switch.

Matching a real Korean 2-set keyboard

The Korean option relabels the letter positions in this full-size ANSI diagram with standard 2-set (두벌식) jamo such as ㅂ, ㅈ, ㄷ, ㄱ and ㅅ. That lets you confirm that an alphanumeric key reports its expected physical position even if your operating system input language is different. ISO, compact and laptop keyboards can have a different physical shape, and Fn or media keys often never reach the browser, so this diagram cannot test those keys.

Frequently asked questions