Keyboard testerEvery key, rollover and chatter
What it checks
Which keys reach your computer, how many register at once (rollover) and whether any key registers twice (chatter). It runs in this page: nothing you press is sent or saved.
Click here or press Tab to start, then press any key.Listening. Press keys, or hold several at once.
This test reads a hardware keyboard. Connect one, then tap the board and press keys.
Press keys to light them up; the results, the event log and any chatter are listed after the board. Tab and Escape keep working, and Tab moves on to the results.
- Keys tested
- 0of 104
- Held now
- 0
- Most at once
- 0
- Chatter
- 0
- Held
- Tested
- Not tested yet
- Chatter
Last 8 events
| Event | Code | Key | Since previous |
|---|---|---|---|
Chatter
None so far. A key appears here when it registers a new press within the threshold of its release.
Keys outside the diagram
None so far. Media keys, F13 and up and other extra keys appear here by code and value.
Rollover: keys at once
Hold keys down one at a time and watch Most at once. The keyboard, its connection, the system and the browser each decide what reaches this page.
Add keys one by one
Keep every key held and press one more. When a new key stops lighting up, the count has reached a limit somewhere between the keys and this page.
Try other combinations
Some keyboards stop at particular combinations rather than at a fixed number, so repeat the test with keys from other rows and both hands.
Read it honestly
A count that stops is what this browser received, not proof of the keyboard's own limit: some combinations never reach a web page at all.
Chatter: one press, two registrations
The tester flags a key when a new press arrives within the threshold after that key's release, and shows the gap in milliseconds.
It detects the symptom, not its cause. A quick deliberate double tap can look the same, so lower the threshold if real double letters are flagged, and retest a flagged key slowly before you decide the switch is at fault. Holding a key down makes your system repeat it; those repeats are never counted as presses or as chatter.
What a web page cannot see
The browser only receives what the keyboard and the system pass on. Shortcuts keep working here; nothing is blocked.
Keys kept before the browser
Fn is usually handled inside the keyboard, and some media, brightness or system keys are taken by the system. They may never light up here even when they work.
Browser shortcuts still act
In most desktop browsers F5 reloads the page and F11 switches to full screen, so test those keys last. In Firefox, / and ' open Quick Find: press Escape, then click the board.
On a Mac
Keys pressed while Command is held do not report their release, so the tester releases them when Command comes up. Caps Lock reports turning on and off rather than being held: it counts as a press each time, never as held.
When keys stop lighting up
The page has lost focus, often to a menu or another window. Click the board to carry on; the keys already tested stay marked.
Frequently asked questions
Is anything I press sent anywhere?
No. The test runs entirely in this page: key presses, timings and results stay on your device and are gone when you leave the page or press Reset. Once the page has loaded it needs no connection.
What does "Most at once" mean?
It is the largest number of keys this page saw held down at the same time: the rollover your keyboard, its connection and your system delivered to the browser. A keyboard with N-key rollover should keep counting as you add keys. If the count stops early, try other key combinations, another port or another browser before you blame the keyboard.
What is key chatter?
One press that registers as two or more. The tester flags a press that arrives within your threshold after the same key was released and shows the gap in milliseconds. It cannot tell why it happened: retest the key slowly, and if it keeps registering twice, the key needs attention. Browsers with strict privacy settings round event times, which makes short gaps less precise.
Why does a key not light up?
Either the key never reached the page or the page was not listening. Click the board first. Some keys are handled by the keyboard or the system before a browser sees them, such as Fn and some media keys. If an ordinary letter or number never lights up in any app, the key itself is the likely fault.
Why do the labels differ from my keyboard?
The board lights physical positions, so a key lights up where it sits whatever its label says. Choose your layout and shape to match the labels: ANSI boards have a wide Enter, ISO boards a tall one and an extra key beside the left Shift. Keys the diagram does not draw appear under "Keys outside the diagram".