Keyboard Double Click Test
Check whether a key registers one press as two. Click the pad below and press the suspect key at a normal pace: the test times the gap between same-key presses and flags any too close together to be intentional — the tell-tale sign of a worn switch “chattering” one keystroke into a double.
Holding a key down is ignored — OS auto-repeat never counts as chatter.
Click this pad to focus it, then press the suspect key at a normal pace.
Press a key a few times to begin.
Per-key results
No keys tested yet — each key you press gets its own verdict here.
Press log
most recent firstNo intervals yet — press the same key twice or more.
Keyboard chatter — or double typing — is a hardware fault where one key press registers as two or more keystrokes. As the switch under the keycap wears or collects dust and oxidation, its contacts bounce instead of settling cleanly, so a single press makes, breaks, and re-makes the circuit. Firmware is meant to filter that bounce for a few milliseconds (a delay called debounce), but on an ageing switch the bounce outlasts the filter and a second keystroke slips through. The fault gets worse over time, and usually hits one or two keys long before the rest.
This test catches chatter by timing your keystrokes. Each press gets a high-resolution timestamp, and the tool measures the gap to your previous press of the same key — different keys never mix, so you can check several suspects in one session. Holding a key is safe: OS auto-repeat is detected and ignored, so it can never show up as a false fault. The check is live, so you can drag the threshold slider afterwards and watch the flags update. Everything runs locally — no keystrokes leave your device.
A deliberate same-key double press — the “ll” in “hello” — almost never lands under 100 ms, even from a fast typist. Chatter is far faster, usually under 50 ms and often single digits, because it comes from electrical bounce, not finger movement. That is why a 50–80 ms threshold separates the two cleanly: real double presses sit above it, chatter well below. One stray flag can be noise; repeated flags on the same key in the low tens of milliseconds mean the switch is failing.
Typical same-key intervals
| Interval | Typical source | What it means |
|---|---|---|
| Under 10 ms | Electrical contact bounce | Almost certainly chatter — no finger repeats a key this fast |
| 10–50 ms | A worn or dirty switch | The classic chatter range; very likely a misfire |
| 50–100 ms | Severe chatter or very fast typing | Grey zone — retest that key slower to be sure |
| 100–300 ms | An intentional double press | Normal — fast typists hit double letters in this range |
| Over 300 ms | Relaxed repeated presses | Normal typing pace |
How to fix a chattering key?
- Confirm the fault — run the Keyboard Tester to check every key registers, so you know the chatter is isolated to one switch before opening anything up.
- Update the firmware — manufacturers ship chatter fixes, and boards running QMK or VIA let you raise the debounce time to mask mild bounce.
- Clean the switch — blast the key with compressed air, or work a few drops of contact cleaner in and press rapidly to clear oxidation off the contacts.
- Replace the switch — on a hot-swap board it pulls straight out; on a soldered board, desolder it and fit a fresh one.
- Use the warranty — if the keyboard is still covered, chatter is a recognized fault and usually grounds for a replacement.
A mouse develops the same fault: the micro-switch under a button bounces and one click registers as two. If your mouse double-clicks on its own, run the Mouse Double Click Test — it works just like this page, timed clicks instead of keystrokes.