Keyboard Tester

How to use the keyboard tester

With this page open, press keys one by one. The matching key on screen turns blue while held and green once released. Green means the key registered. Any key that stays white never sent a signal to your computer.

• Pick a layout: ANSI (US), ISO (UK/EU), JIS (Japanese), Mac or Korean. The tester picks one based on your system the first time.
• Pick a size: Full (with numpad), TKL (tenkeyless) or 75% / laptop. Progress is counted against the keys on the selected layout.
• Press every key: when the progress bar reaches 100%, every key works. Use Show remaining keys to list the ones you missed.
• Check rollover: hold several keys at once to see how many are recognized.
• Check chatter: tap a suspicious key slowly several times. If one press registers twice, the key turns red with a counter.
• Copy result: copy a short text summary for a warranty claim or a second-hand sale listing.

What is key chatter and how to fix it

Key chatter is when one press registers as two or more, so you type "helllo" or a game ability fires twice. Switch contacts bounce briefly when they close and open, and keyboard firmware normally filters this out. Dirt or worn contacts can make the bounce slip through as an extra keystroke.

This tester measures the time between releasing a key and pressing it again, in milliseconds, and flags anything shorter than the threshold (30 ms by default). A higher threshold is more sensitive, but set it too high and deliberate fast double taps will be flagged too. Changing the threshold re-evaluates every press already recorded.

• Confirm it is reproducible: press the key slowly 10+ times. One or two flags may just be fast tapping.
• Try another USB port or another computer to separate keyboard problems from PC or cable problems.
• Pull the keycap and blow out dust with an air blower. After a spill, unplug the keyboard and follow the manufacturer’s instructions.
• If your keyboard software has a debounce time setting, raising it slightly can hide chatter, at the cost of possibly dropping very fast repeated taps.
• On a hot-swap board you can replace just the faulty switch. For soldered boards or devices under warranty, contact the manufacturer.

N-key rollover, 6KRO and ghosting

Rollover is how many simultaneously pressed keys a keyboard reports correctly. With N-key rollover (NKRO) every key is scanned independently, so any number of keys register. The USB HID boot keyboard protocol reports modifier keys separately plus at most six other keys, so keyboards using it are limited to six non-modifier keys, often called 6KRO.

Keyboards wired as a row-and-column matrix can show ghosting: pressing three keys at the corners of a rectangle makes a fourth, unpressed key appear. Many modern keyboards avoid this by ignoring the third key instead, which is called key blocking or jamming. If keys drop only in certain combinations, it may be a design limit rather than a fault.

Test with the combinations you actually use: W A S D plus Shift, Space and Ctrl for games, or overlapping keys from both hands for typing. An extra key lighting up means ghosting; a held key not lighting up means blocking.

Layouts: ANSI, ISO, JIS, Mac and Korean

Keys are identified by event.code, which describes the physical position, so the tester works no matter which input language is active.

• ANSI (US): a single-row Enter and a long left Shift.
• ISO (UK/EU): a tall two-row Enter and an extra key next to the left Shift (IntlBackslash).
• JIS (Japanese): extra keys such as ¥, ろ, 無変換 (NonConvert), 変換 (Convert) and かな (KanaMode).
• Mac: control, option (⌥) and command (⌘) placement. The 75% size shows a MacBook-style arrow cluster.
• Korean: Hanja (Lang2) and Han/Yeong (Lang1) keys beside the space bar. On some keyboards these send right Ctrl and right Alt instead, and the tester relabels those keys when that happens.

Reading the key event log

The log shows exactly what the browser received for the last 40 events, which is handy for remapping or web development.

• key: the value the key produces, which changes with Shift and input method (for example "a", "A" or "Process").
• code: the physical key position, such as KeyA, independent of the active layout.
• keyCode: the legacy numeric code. It is deprecated in the standard but still widely used.
• location: 0 standard, 1 left, 2 right, 3 numpad, to tell apart keys like left and right Shift.
• Auto-repeat from holding a key is folded into one row with a ×count and excluded from progress and chatter detection.

Keys browsers cannot test

These are limits of browsers and operating systems, not faults in your keyboard.

• Fn: usually handled inside the keyboard hardware, so it never reaches any web page. It is shown dashed and excluded from progress.
• Reserved shortcuts: Chrome handles tab and window shortcuts (Ctrl+W/T/N, Ctrl+Tab, Alt+F4) before the page sees them, and the OS takes Alt+Tab, Win key combos and Ctrl+Alt+Del. Press these keys on their own instead of in combination.
• Fullscreen test: in Chrome and Edge, fullscreen passes most tab and window shortcuts to the page, and keyboard lock can capture system keys like Alt+Tab, Win and Esc where the OS allows it. Press and hold Esc to exit. Firefox and Safari do not support keyboard lock.
• Print Screen and media keys: keys the OS handles first may arrive only partly or not at all. A key-up alone still counts as tested here.