Keyboard Chatter / Double Click Test

How to use

1. Use the recommended Selected-key check for one suspect key, or Broad scan to identify codes worth retesting. Select 20, 30, 50, or 100 completed press cycles and a 30, 50, 80, or 100 ms screening window.
2. Press Start, then press the suspect key first. In Selected-key check, that first fresh non-repeat keydown becomes the target for the run.
3. Use deliberate press-and-release cycles. Do not hold keys when trying to reproduce double typing; browser auto-repeat is excluded separately.
4. Let the cycle goal finish the run or use Stop. Review keydown-before-release anomalies, short post-release flags, per-key observations, and the current-run timeline.
5. Repeat suspicious results using the same mode, screening window, keyboard, connection, browser, and similar tapping style. Compare aggregate local history rather than treating one flag as a diagnosis.

What the result means

• A completed press cycle is a fresh non-repeat keydown followed by keyup.
• A possible duplicate keydown is one fresh browser keydown that matches at least one screening condition. Each fresh keydown can count at most once, even when multiple suspicious conditions apply.
• Keydown-before-release means the browser delivered another fresh same-code keydown before a keyup closed the previous browser-observed press. It can reflect duplicate registration, a missed keyup, remapping/software, or connection and event-delivery behavior; it is not automatically switch chatter.
• A short post-release flag means a completed press/release cycle was followed by another fresh same-code keydown within the selected screening window. It can be unwanted registration or an intentional fast re-press, and remains a timing screen rather than a hardware verdict.
• The possible-duplicate ratio is unique flagged fresh keydowns divided by accepted non-repeat keydowns. Separate minimum intervals show the shortest browser-observed evidence for each anomaly class.
• KeyboardEvent.repeat=true marks automatic held-key repetition. Repeat events are reported separately and excluded from suspected duplicate detection and fresh-press chatter screening.
• Per-key observations show which physical KeyboardEvent.code produced the browser-level pattern. A flag is screening evidence, not confirmation of a failed switch.

Limitations

• Possible duplicate browser events are screening evidence only. Fast intentional taps, remapping/software, connection behavior, or missing events can mimic chatter; the page cannot inspect switch contacts or firmware debounce.
• Browser events arrive after keyboard firmware, debounce logic, connection, operating system, and browser processing. The page cannot observe switch contacts or read the configured firmware debounce algorithm or time.
• The 30, 50, 80, and 100 ms values are browser-side screening windows, not universal hardware thresholds or firmware settings. Intentional fast re-presses can fall inside larger windows.
• Remapping software, macros, accessibility tools, virtual machines, remote desktop, firmware behavior, connection issues, missed events, and browser scheduling can change the observed pattern.
• No flags observed in one run cannot prove that a switch has no intermittent problem. A Broad scan total cycle goal is spread across the keys pressed and is not a per-key sample guarantee.

Troubleshooting

Many intentional taps are marked possible duplicates

Use slower, clearly separated press-and-release cycles or a shorter screening window. Larger windows intentionally classify more fast re-presses as possible duplicates.

The selected key is not the one expected

Reset, choose Selected-key check, press Start, and make the intended key your first fresh non-repeat press.

A key only double-types occasionally

Repeat the suspect key in Selected-key mode with deliberate slow press/release cycles. Compare another browser and, where practical, another port, connection, or computer. Intermittent behavior may not appear in a short sample.

The run was interrupted

Focus loss or page hiding invalidates the run for history. Return to the page and start a fresh capture.

The page shows a flag but typing seems normal

Treat it as browser-level screening evidence. Repeat the setup, then consult manufacturer or firmware documentation for supported debounce settings and follow manufacturer cleaning or service instructions if the behavior persists.

Related tools

• Keyboard Tester

  Test keyboard keys online across common Windows, Mac, and compact layouts. See pressed and detected keys, event.key/event.code, repeat state, simultaneous browser input, and untested keys.

• Keyboard Rollover Test

  Test keyboard rollover with free and guided key combinations. See max simultaneous keys, best match, possible missing or unexpected codes, with clear NKRO and ghosting limits.

• Keyboard Event Timing Test

  Compare browser-received keyboard event timing with controlled tapping, alternating-key, and OS auto-repeat runs. Review intervals, cadence, consistency, and local history—not USB polling.

• Mouse Double Click Test

  Check a mouse for unintended repeat clicks with slow single-click screening. Inspect browser-observed intervals by button, then optionally measure intentional double-click timing.

FAQ