Keyboard Chatter / Double-Press Test

How to use

1. Choose Selected-key check for one suspect key or Any-key scan for a broader session. Select 20, 30, or 50 completed press cycles and a 30, 50, 80, or 100 ms screening window.
2. Press Start. In Selected-key check, your first fresh non-repeat keydown becomes the target.
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 per-key observations, possible duplicate keydowns, minimum suspicious gap, 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.
• The possible-duplicate ratio is flagged fresh keydowns divided by accepted non-repeat keydowns. Minimum suspicious gap is the shortest interval associated with a flagged event.
• 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.
• A clean run cannot prove that a switch has no intermittent problem. An Any-key total cycle goal 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 several controlled runs on that key. Intermittent behavior may not appear in a short sample; compare local history instead of treating one clean run as proof.

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 same key and setup before investigating firmware, connection, software, or hardware causes.

Related tools

• Keyboard Tester

  Test keyboard keys online with Windows full-size, TKL, MacBook/Apple, and 60% layouts. See pressed/tested keys, event.key/event.code, repeat status, 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 Polling Rate Test

  Check browser-observed keyboard event timing in single-key, alternating-key, and auto-repeat modes. See event Hz, intervals, consistency, and local history—not raw USB polling.

• Mouse Double Click Test

  Test a mouse for unintended double clicks with slow single-click screening or intentional pair timing. Choose a button, inspect browser click intervals, and compare local runs.

FAQ