Stuck Key Test — Held, Repeating & Dropped Keys
This stuck key test tells you in seconds whether a key is jamming, repeating on its own, or silently dropping out while you hold it. Press and hold any key in the panel above: the trace stays solid while the signal is continuous, and draws a red gap the moment your computer sees the key release and re-press. Every break is logged with its duration in milliseconds, so you leave with evidence instead of a hunch.
How to test for a stuck key
Start with the key you suspect. Hold it for five to ten seconds: the readout should say Holding the whole time and the trace should stay unbroken. If it flickers back to idle, or a red gap appears, that key is losing contact mid-press.
Then do the opposite test: tap the key once and let go. The signal must drop to idle and stay there. A key that keeps sending input after your finger has left it is stuck — mechanically, electrically or in software. Compare the suspect key against a neighbouring key you trust; the difference is usually obvious within one hold.
If you do not yet know which key is at fault, run the full keyboard tester first to find the misbehaving key, then come back here to hold it and watch the signal.
Setting the drop threshold
The threshold slider (10–250 ms, 80 ms by default) decides how short a break has to be before it counts as a dropout rather than you genuinely releasing the key. At 80 ms, anything quicker than a deliberate re-press gets flagged. Drop it to about 30 ms if you only care about severe interruptions; raise it toward 150 ms when you are hunting an intermittent wireless link and want every flicker on record.
What this test cannot detect
A browser only sees keydown and keyup events after the keyboard firmware and your operating system have already processed them. Any dropout shorter than the keyboard's internal debounce window — typically around 5 ms — never reaches this page, so a clean stuck key test means "clean as far as the OS is concerned", not "electrically perfect". The page also cannot tell you which physical switch under a laptop keycap is failing.
Why a keyboard drops keystrokes
Dropped keystrokes have three common causes, and each leaves a different fingerprint. A worn switch loses contact for a few milliseconds in the middle of a hold — short red gaps that cluster on one key and nowhere else. A stalling wireless link loses whole keystrokes: as one forum poster put it, you hear the click, so the key was not missed, but "something's not connecting". A software fault drops keys at random across the whole board, including the on-screen keyboard, which rules hardware out immediately.
A fourth failure looks like dropping but is not: on a low-cost membrane board, some key combinations cannot be reported simultaneously, so the third or fourth key you hold never registers. That is a key matrix limit, not a fault.
The mirror-image problem — one press producing two characters — is chatter, not a dropout, and it needs a different measurement. Use the keyboard double click test for that: it times the gap between two separate presses, where this page times the gap inside a single hold.
Key repeat rate and repeat delay
When you hold a key, it is your operating system that starts repeating it, not the keyboard. Two settings control the behaviour. Repeat delay is how long you must hold before repetition begins — usually between 250 ms and 1 second. Repeat rate is how fast characters arrive once it has begun, commonly 2 to 30 characters per second.
The distinction matters for diagnosis. A key that runs away the instant you touch it points at a repeat delay set far too short. A key that keeps typing after you release it is a genuine stuck key, and no slider will fix it. The stuck key test above filters out auto-repeat entirely — repeated keydown events that carry the repeat flag are ignored — so what the trace shows is the real state of the key, not your OS repeating on your behalf.
Wireless 2.4 GHz and Bluetooth dropouts
The 2.4 GHz band is shared with Wi-Fi, Bluetooth, noisy USB 3.0 ports and microwave ovens, so a wireless keyboard can drop keystrokes for reasons that have nothing to do with its switches. Before you blame the board:
- Move the receiver onto a front port or a short USB extension — a metal case between dongle and keyboard costs real range.
- Keep the dongle away from USB 3.0 ports and external SSDs; both radiate straight across 2.4 GHz.
- Change the batteries even when the indicator looks fine. Falling voltage causes retries long before a low-battery warning appears.
- Prefer the 2.4 GHz dongle over Bluetooth if the keyboard supports both. Bluetooth adds a power-saving sleep state that can swallow the first keystroke after an idle pause.
- Re-test wired. If a cable makes the problem vanish, the switches are fine and the radio link is the culprit.
To reproduce a dropout on demand, hold W here and walk the keyboard away from the receiver. A radio problem shows up as gaps that grow with distance; a switch problem does not care where you stand.
If keystrokes arrive but arrive late rather than going missing, that is input lag, not a dropout — measure it with the keyboard latency test instead.
Changing repeat rate on Windows and Mac
If the stuck key test comes back clean and only the repeat behaviour feels wrong, both systems let you retune it in a minute.
Windows 10 and 11
Press Win + R, type control keyboard and press Enter. The Speed tab holds both sliders — Repeat delay and Repeat rate — with a test box underneath. Windows 11's Settings app still has no equivalent page, so this Control Panel applet remains the built-in route. Changes take effect immediately, no reboot.
While you are there, open Accessibility and check Filter Keys. Filter Keys deliberately ignores brief or repeated keystrokes, and switching it on by accident is a very common reason for "my keyboard started skipping letters".
macOS
Open System Settings, then Keyboard, and drag Key repeat rate and Delay until repeat to the fast end. The sliders stop at a repeat interval of roughly 30 ms and an initial delay of roughly 225 ms. Terminal goes further than the GUI allows: defaults write NSGlobalDomain KeyRepeat -int 1 and defaults write NSGlobalDomain InitialKeyRepeat -int 10, then log out and back in. Both values are counted in 15 ms ticks, so KeyRepeat 1 is about one character every 15 ms.
If holding a key produces an accent menu instead of repeating at all, press-and-hold accent input is enabled. Turn it off with defaults write -g ApplePressAndHoldEnabled -bool false and restart the app.
Frequently asked questions
Random keys act like they're stuck even though they're not physically pressed. What causes that?
Almost always software, not the switch. The giveaway is that the problem follows you to a second keyboard and to the on-screen keyboard, but disappears on the Windows lock screen. A modifier — Shift, Ctrl, Win or Fn — gets latched because its keyup event was lost, usually by a USB driver or a remapping utility. Sign out and back in to clear it, then tap each modifier once and re-test here.
When I hold any key on my keyboard down and let go, it keeps going. How do I stop it?
Tap the key once, square on, and watch this page: if the trace stays active after you release, the keyup never arrived. On a laptop that usually means debris under the keycap — spilled soda leaves a key tacky, and W and Space are the usual victims. Blow it out with canned air and work the key 20–30 times. If every key behaves this way, it is the driver: remove the keyboard in Device Manager and reboot.
Why does my keyboard skip characters when I type?
Because the keystroke is being lost after the switch closes, not before. If you hear and feel the click but no character appears, the switch did its job and the link to the PC dropped the report. On wireless boards that means interference or a weak battery; on wired boards it is usually a hub or a damaged cable. Plug straight into a rear USB port on the motherboard and hold a key here for a few minutes.
Why does my wireless keyboard miss certain keys when I'm gaming?
Holding several keys at once is the hardest thing you can ask of a wireless link, so dropouts surface in games first. Hold W here and move the keyboard away from the receiver: a red gap means the radio link broke, not the switch. Move the dongle to a front port away from USB 3.0 devices, fit fresh batteries, then retest wired. A clean ten-minute wired run points squarely at the radio.
How do I change the keyboard repeat rate and repeat delay in Windows 11?
Press Win + R, type control keyboard and press Enter — the Speed tab has both sliders. Repeat delay sets how long you hold before repetition starts; repeat rate sets how quickly characters come once it does. A test box sits under the sliders so you can try the new speed before saving. Windows 11's Settings app has no equivalent page, so the Control Panel applet is still the way. Changes apply instantly.
How do I make the key repeat rate faster on a Mac?
Push both sliders in System Settings → Keyboard to the fast end first; if that is still too slow, Terminal goes beyond what the GUI exposes. Run defaults write NSGlobalDomain KeyRepeat -int 1 and defaults write NSGlobalDomain InitialKeyRepeat -int 10, then log out and back in. The units are 15 ms ticks, so KeyRepeat 1 is roughly one character every 15 ms against the slider's 30 ms floor.
Is Sticky Keys the same thing as a stuck key?
No. Sticky Keys is a Windows accessibility feature that lets you press Ctrl, release it, then press C instead of holding both at once — and pressing Shift five times switches it on by accident. A stuck key is hardware or lost input: the key keeps sending signal with nobody touching it. If turning Sticky Keys off changes nothing, and this test still shows the key held while your finger is away, it is not Sticky Keys.