Keyboard Double Click Test
Find chattering keys that type twice from one press. Click the test area, type normally, and see per-key timing, a heatmap of your keyboard and every press that came back too fast for a human finger.
Waiting for key presses
A gap under 40 ms after release, a second keydown with no keyup under 40 ms after the previous keydown, or a press shorter than 25 ms, is flagged. Fast human double taps rarely beat 60 ms.
Type this sentence
The quick brown fox jumps over the lazy dog
How this key chatter test works
What key chatter is
Chatter is a key typing twice (or more) from one press. A switch is two metal contacts, and they bounce for a few milliseconds when they meet. Keyboard firmware waits out that bounce, a step called debounce. When the contacts wear, get dirty or oxidise, the bounce lasts longer than the firmware waits, and one press reaches the computer as two. Mechanical switches are the usual victims, often a single well-used key like E or Space, but some keyboards ship with debounce set so low that new switches chatter too.
Reading the result
For every keydown the test measures how long ago that same key was released. A deliberate double tap takes most people 60 ms or more between release and the next press. A gap under the threshold (40 ms by default, 10 to 100 ms on the slider) is flagged. A second keydown with no keyup between them is flagged when the time since the earlier keydown is under that same threshold. A press shorter than 25 ms is faster than a finger, so it is flagged too; if the threshold is under 25 ms, that cutoff drops to the threshold. One flag in hundreds of presses can be a fluke; the same key flagging again and again is a failing switch. Raise the threshold to be stricter, lower it if fast typing gives false alarms. Times come from the browser, which can add a millisecond or two of jitter. Mobile on-screen keyboards report keys poorly, so use a physical keyboard.
Chatter or key repeat?
Holding a key makes the operating system repeat it after a delay. That is the key repeat setting, not a fault, and the browser marks those events as repeats. This test ignores them for chatter and counts them separately in the Autorepeats tile. If letters double only when you hold a key, shorten the hold or increase the repeat delay in your OS keyboard settings.
How to fix a chattering key
- Blow compressed air under the keycap while pressing the key repeatedly.
- Pull the keycap and work the switch a few hundred times, or clean it with contact cleaner.
- On hot-swap boards, swap the switch with a rarely used one to confirm, then replace it.
- Raise the debounce time in the vendor's keyboard software or firmware, if it offers one.
- As a stopgap on Windows, community chatter-filter utilities drop repeated presses that arrive too quickly.
Warranty claims
Switches are rated for tens of millions of presses, so chatter within the warranty period is a defect the maker should cover. Run the test, screenshot the flagged events and per-key table, and send them with your claim. Repeated flags on one key are hard to argue with.
Related tools
Check whether several keys register together with the keyboard ghosting test. The mouse version of this test is the double click test. Count presses with the spacebar counter or test your speed with the click speed test.
Frequently asked questions
What does this test count as chatter?
Three timings are flagged, and a press is counted once. The same key goes down again under the threshold after it was released. A second keydown arrives with no keyup between them, and the time since the earlier keydown is under that threshold. Or the press lasted under 25 ms, or under the threshold when the threshold is below 25 ms. A gap flag wins over a short-press flag, and a short press followed by a gap flag is not counted again. The default is 40 ms, and the slider runs from 10 ms to 100 ms. A higher number flags more presses.
Does holding a key count as chatter?
No. Holding a key makes the operating system repeat it, and the browser marks those later keydowns as repeats. This test does not score repeats as chatter. It counts them in the Autorepeats tile, and the per-key table shows a repeat count beside the key. If letters double only while you hold a key, shorten the hold or increase the repeat delay in your OS keyboard settings.
Are results saved?
No. Presses, flags, repeat counts and the sentence you typed stay on this page until you press Reset or leave. Only the latest 5000 presses are kept in memory. The only value saved on this device is the threshold, so the slider can reopen at the same setting. Nothing is uploaded.
Why can one tap show up as two keydowns?
A worn, dirty or oxidised switch can bounce longer than the keyboard firmware waits, so one press reaches the computer as two keydowns. Those two are either separated by a keyup that comes too soon, or the second keydown arrives with no keyup. One flag can be a fluke or a very fast tap. The same key flagging again and again is the switch to check.
Does the sentence box use the same timing?
Yes. Keys typed there are timed with the same rules and show up in the per-key table and the flagged list. Drawn keys also show on the heatmap. The box marks a letter that repeats the letter before it when that pair is not in the sentence. The quick brown fox sentence has no double letters, so a marked letter is a typo or a chattering key.
Will a phone keyboard work?
Use a physical keyboard. On-screen keyboards report keys poorly. Click or Tab to the dashed area, tap each key a few times without holding, then press Escape or click away to stop. Tab, Space, arrows and / are captured while that area is focused, so Escape is how you leave it from the keyboard.
What does Reset clear?
Reset clears presses, chatter flags, autorepeat counts and the sentence. It does not change the threshold. Moving the slider recomputes flags from the presses already kept, so you can raise or lower the threshold without typing again. Keys that are not drawn on the heatmap still appear in the per-key table. When more than 100 events are flagged, the list shows the latest 100 and the chatter count still includes every flag.