Broken Key Detector

What is this tool?

The Broken Key Detector is built around one question: does this key produce an event every single time you press it? Rather than leaving you to eyeball a diagram, it walks you through the board key by key and keeps a record of what answered and what did not.

Two modes sit on the same page. The plain pass asks you to press each physical key once and marks off what it hears. Guided mode drives the order for you, so nothing gets skipped on a board you do not know well.

When a key looks suspicious the page raises a Possible Key Issue Detected panel. That is a prompt to investigate, not a verdict — the consistency test exists to turn a suspicion into evidence.

How to use it

1. Start the passPress START KEY TEST. The diagram clears and the counter resets. Everything you press from here is recorded against the key it belongs to.
2. Or let guided mode drivePress TEST ALL KEYS to walk the board in order. Next, Previous and Skip Key move through the queue, and Exit Guided Mode hands control back to you at any point.
3. Watch the event logThe log lists every keydown and keyup. Use the ALL, KEYDOWN, KEYUP and PROBLEMS filters to narrow it, and Clear to start a fresh log without losing the diagram.
4. Re-test anything doubtfulSelect the key, then press Test Consistency for Selected Key and START CONSISTENCY TEST. Tap the same key repeatedly and the tool counts how many of your presses actually arrived. FINISH TEST ends the run.
5. Record the outcomeAfter a consistency run you can CONFIRM AS PROBLEM, MARK AS UNTESTED or TEST AGAIN. Confirming keeps the key flagged in the summary so you can quote it to a warranty desk.

What the results mean

A key that never lights up

No keydown arrived at the browser. That is consistent with a failed switch, but it is also what happens when the key is remapped in firmware, intercepted by the operating system, or absent from your layout. Rule those out before blaming the hardware.

Possible Key Issue Detected

The tool saw something irregular — usually a press with no matching release, or a release with no press. It is a flag for follow-up, which is exactly what the consistency test is for.

Consistency below 100%

You pressed the key ten times and fewer than ten events arrived. An intermittent key is the classic early symptom of a dying switch or a contaminated contact, and it is far more convincing evidence than a single miss.

A clean sweep

Every key you pressed produced a matching keydown and keyup. Your keyboard is delivering complete events to the browser, which is as much as software on this side can confirm.

What it can detect

• Keys that produce no event at all
• Keys that answer only some of the time, measured as a hit rate over repeated presses
• Presses with no matching release, and releases with no matching press
• Keys you have not covered yet, so a sweep is genuinely complete

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 missing event is not proof of a broken switch. The page says so in its own FAQ. Firmware remapping, an OS-level shortcut, or a key your layout does not have will all look identical from inside a browser.
• The tool cannot see contact resistance, switch travel or solder joints. It reports what reached the browser and nothing deeper.
• Keys reserved by the operating system — some Fn combinations, and shortcuts the OS swallows first — may never reach the page.

Tips

• Run the consistency test at least ten presses deep. Intermittent faults hide behind small samples.
• Test the same key on a second machine or with a second cable before concluding the keyboard is at fault.
• If several keys in one row or column fail together, suspect the matrix or the ribbon cable rather than individual switches.

Troubleshooting

Related documentation

• KeyboardOnline Keyboard TestThe keyboard tester on the home page — press keys, watch them light up.
• KeyboardStuck Key DetectorWatches for keys that go down and never come back up, with an adjustable hold threshold.
• KeyboardKey Press TestTimes each press: how long you held it, and how long since the last one.
• KeyboardKeyboard Double-Click TestApplies a millisecond threshold to press-to-press timing and calls out chatter.
• KeyboardKey Event TesterA live inspector for event.key, event.code, location, repeat and modifier state — built for developers.