Keyboard Chattering Test
A key that is pressed again less than 40 ms after you released it is flagged as keyboard chattering. A normal deliberate re-press takes well over 80 ms.
How to use
- Click the test area once so it has focus. Typing inside a text field elsewhere on the page is not recorded.
- Press the key you suspect, release it fully and wait about a second. Repeat 20 to 30 times, then try the next key.
- Read the table. A key with suspect presses has been pressed again within the limit after you let it go.
- Change the limit if you want a stricter or looser check. Press Reset to start over.
How it works
The tool records the browser timestamp of every keydown and keyup. Holding a key makes the keyboard send repeated keydown events, and these are ignored.
The gap is the time from a key being released to the same key being pressed again. A gap shorter than the limit (40 ms by default) is counted as a suspected chatter, because a person cannot lift and press the same key that fast on purpose. A gap exactly equal to the limit is not counted.
The hold time is the time between keydown and keyup of one press, averaged per key. It shows how long you hold keys, and it helps you spot a key that releases too early.
The result is a hint, not a hardware diagnosis. Fast typists who roll the same key quickly, such as a double letter, can produce short gaps without any fault.
What keyboard chattering is
Chattering is when one press of a key registers as two or more. The metal contact inside a worn or dirty switch bounces for a moment before it settles, so the keyboard sees the key close, open and close again. You notice it as doubled letters, a space that appears twice, or a key that sometimes ends a held press early.
Every keyboard filters this bounce with a short debounce delay in its firmware. Chattering shows up when the bounce lasts longer than that delay, which happens as a switch ages or when it is damaged by liquid or dust.
How to run the check
- Press each suspect key slowly 20 to 30 times, with a pause of about a second between presses. A flagged press at that pace is a real fault candidate.
- Test the keys that you notice typing twice first, usually the ones you use most.
- Try pressing at the edge of the keycap and with different force, since a worn switch can fail only at some angles.
- If a key chatters, clean under the keycap with compressed air, try a different keyboard for comparison, and consider replacing the switch if the board is hot-swappable or still under warranty.
Reading the gap
| Gap before the next press | Meaning |
|---|---|
| Under 20 ms | Almost certainly contact bounce, not a human |
| 20 to 40 ms | Very likely chatter |
| 40 to 80 ms | Possible chatter or an extremely fast re-press, check by repeating |
| Over 80 ms | A real, intended second press |
FAQ
What limit should I use?
The default is 40 ms. Other online chatter tests use limits such as 45 ms or 80 ms. A lower limit only flags clear faults, a higher one also catches mild chatter but can flag fast intentional presses. If a key keeps getting flagged at 40 ms, it is almost certainly faulty.
My keyboard flagged a key once. Is it broken?
One flag can be a very fast double letter or a slip. Repeat the slow press test. If the same key is flagged again and again at a slow pace, the switch is likely faulty.
Why are the arrow keys, Tab or F5 not doing anything?
While the test area has focus, the page blocks the normal action of keys so scrolling or shortcuts do not get in the way. Tab still moves the focus out of the area. Click outside the area to use the keys normally again.
Does it work for the keys of a laptop or a phone?
Laptop keyboards work like any other. On-screen keyboards on phones and tablets do not send key events in a reliable way, so connect a physical keyboard. Fn and many media keys never reach the web page.
Is anything sent to a server?
No. The timing is calculated in your browser and kept only in memory until you leave the page. Avoid typing passwords here anyway.