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Keyboard Double-Click Test
Applies a millisecond threshold to press-to-press timing and calls out chatter.
- Available — Live on this site right now.
- Browser Tool — Runs in the browser you are reading this in.
- No Install — Nothing to download, no extension, no account.
- Client-Side — Runs entirely on your device. No test data is uploaded.
- Desktop — Needs a physical keyboard or mouse to be useful.
This page explains the tool. The tool itself is one click away and needs no sign-in.
Open Keyboard Double-Click TestWhat is this tool?
Chatter is when one physical press produces two electrical signals. You press a key once and get two characters. This page measures the gap between consecutive presses of the same key and flags any gap shorter than your chosen threshold.
Mechanical contacts bounce for a fraction of a millisecond when they close. Keyboard firmware hides that behind debounce — a short window during which further transitions are ignored. When a switch ages, its bounce outlasts the debounce window and the second signal escapes.
That is why this test is a timing test and not a counting test. Two presses 8 ms apart are not fast fingers; they are one press reported twice.
How to use it
- Choose a sensitivitySix thresholds are offered: 40 ms Very sensitive, 60 ms Sensitive, 80 ms Normal (the default), 100 ms Relaxed, 120 ms More tolerant and 150 ms Very tolerant.
- Press the suspect key deliberatelySingle, separate taps — one press, pause, one press. Do not try to type quickly; the point is that every gap you create should be far wider than the threshold.
- Repeat twenty or thirty timesChatter is intermittent. A key that misbehaves once in fifty presses will pass a short test and still ruin your typing.
- Read the flagged pairsAny pair closer together than the threshold is listed with its actual interval in milliseconds. That number is your evidence.
What the results mean
A flagged pair at 5–20 ms
Almost certainly chatter. No human produces two deliberate presses that close, so the second signal came from the switch or from the firmware's debounce failing to suppress it.
A flagged pair at 60–80 ms
Ambiguous. That is within reach of a fast double tap, especially on a lighter switch. Lower the threshold to 40 ms and try again — if it still flags, take it seriously.
Nothing flagged
No press-to-press interval fell below your threshold during the session. Raise the sensitivity to 100 ms or more and repeat if you are still suspicious; that widens the net at the cost of more false positives.
Why the threshold matters
The threshold is the line between “too fast to be real” and “fast typing”. A tighter threshold gives you fewer, more certain flags; a looser one gives you more flags that need judgement.
What it can detect
- Two key events from a single physical press, with the interval reported in milliseconds
- How often chatter happens, over as many presses as you care to make
- Which specific key is affected
- Whether tightening the threshold makes the flag go away, which is the fastest sanity check
Limits worth knowing
A browser can only report what the platform gives it. These are the honest boundaries of this page, so a result is never read as more than it is.
- A flagged pair is strong evidence, not certainty. The page says so itself. Software — a macro tool, a remote-desktop session, an accessibility setting — can duplicate a key event with perfectly healthy hardware.
- Operating-system auto-repeat is a separate mechanism. Do not hold the key; a held key produces a legitimate stream of repeats that has nothing to do with chatter.
- The tool cannot see the switch's actual bounce waveform or the firmware's debounce setting. It sees the events that escaped.
Tips
- Start at 80 ms. If a key flags there, drop to 40 ms — a flag that survives 40 ms is very hard to explain as fast fingers.
- Many QMK and VIA keyboards let you raise the debounce time in firmware. That often cures a chattering switch outright and costs nothing.
- If firmware will not fix it, the switch itself is the usual culprit. On a hot-swap board that is a thirty-second repair.
Troubleshooting
Every key flags at 150 ms
That threshold is wider than an ordinary double tap, so normal typing will trip it. Come back down to 80 ms.
One key chatters only sometimes
That is exactly how chatter behaves. Keep testing — an intermittent fault needs a longer sample, not a different tool.
It flags here but I never see double characters
Some applications debounce input themselves, which masks the symptom. The event data is still real, and it will surface in games or in a text editor that does not filter.
How do I fix chatter?
In order of effort: raise the debounce time in firmware if your board supports it; clean the switch contacts with contact cleaner; replace the switch. On a soldered board, replacement means desoldering.
Ready to run it?
Applies a millisecond threshold to press-to-press timing and calls out chatter. Nothing to install, and it opens in this browser.