Stuck Key Detector

What is this tool?

A stuck key is one the computer believes is still pressed after you have let go. It shows up as a runaway character, a game character that will not stop walking, or a modifier that turns every keystroke into a shortcut.

This page watches the keydown and keyup stream and measures how long each key stays down. If a key is held past the threshold without releasing, it is raised as a stuck-key candidate and named.

The threshold is yours to set — 1, 2, 3, 5, 8, 10, 15 or 30 seconds, with 5s as the default. Shorter thresholds catch problems faster but will also flag deliberate long holds.

How to use it

1. Let it watchThe page starts in monitoring mode as soon as it has focus. You do not need to press anything to arm it — the panel reads Ready to Test until the first event arrives.
2. Pick a thresholdChoose how long a key may stay down before it counts as stuck. Leave it at 5s (Default) unless you are hunting something specific; drop to 1s or 2s to catch a briefly latching modifier.
3. Type normally, then stopType a sentence, then take your hands off the keyboard completely. Anything still reporting as held after you have stopped is the thing you are looking for.
4. Read the logFilter with STUCK to see only flagged keys, or REPEAT to isolate operating-system auto-repeat. PAUSE MONITORING freezes the view so you can read it, Clear empties the log and RESET MONITORING starts a clean session.

What the results mean

A key flagged as stuck

A keydown arrived, the threshold elapsed, and no keyup followed. If your hands were off the keyboard, that is a real fault — mechanically stuck, contaminated, or held by software.

Repeat events

A long stream of repeats from one key is your operating system's auto-repeat doing its job, not a fault. The REPEAT filter separates them so they do not muddy the picture.

Flagged while you are holding it

That is correct behaviour. The tool measures hold time and cannot know whether your finger is still down. Release the key and the flag clears.

Nothing flagged

Every press you made was matched by a release within the threshold. No stuck-key behaviour reached the browser during the session.

What it can detect

• Keys held past your chosen threshold with no keyup
• Modifier keys that latch and stay active after release
• Operating-system auto-repeat, shown separately so it is not mistaken for a fault
• Which key is responsible, by name and code

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 stuck result does not automatically mean the keyboard is broken. Sticky Keys, a remote-desktop session that dropped a keyup, a macro utility or a game overlay can all leave a key logically down.
• The tool measures time between events. It cannot see debris under a keycap, a bent stem or a spring that has lost tension.
• Switching browser tabs interrupts the event stream, so the session resets rather than reporting a false stuck key.

Tips

• Take your hands off the keyboard for a full ten seconds before reading the result. Most false positives are a finger still resting on a key.
• If a modifier is the culprit, check the operating system's accessibility settings first — Sticky Keys produces exactly this symptom with perfectly healthy hardware.
• A key that sticks only when warm, or only after heavy use, is worth catching with a longer session rather than a quick check.

Troubleshooting

Related documentation

• KeyboardBroken Key DetectorA guided pass over every physical key, plus a consistency re-test for the ones that look wrong.
• 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.
• KeyboardOnline Keyboard TestThe keyboard tester on the home page — press keys, watch them light up.
• KeyboardKey Event TesterA live inspector for event.key, event.code, location, repeat and modifier state — built for developers.