Keyboard Double Click Test for Keys That Type Twice

Click the box, type slowly and see which keys, if any, fired twice inside the 40 ms window.

Five dozen quick lambs jump over the grey wax hut

0 repeats in 0 presses

Window: 40 ms.

  1. No repeats logged yet. Type slowly.

Keys with repeats: noneIgnored 0 held-key repeats

Press Esc to leave the box. Only the key position and the gap are logged. The box is emptied when the run ends.

More options

Your last five runs

  1. No run yet.

Nothing from this test is stored unless you tick the box. Kept runs are numbers only and never leave this browser.

How this check works

Slow pangram, one key a second

Type "Five dozen quick lambs jump over the grey wax hut" at about one key a second. It presses all 26 letters, and at that pace a second signal 12 ms after the first cannot have come from your finger.

A repeat is a second firing of one key inside the window of its last press, or inside half the window of its release. The window starts at 40 ms. You can change it under More options.

  • A repeat is logged only when a fresh key-down follows a key-up of the same key, inside the window counted from the key-down before it or inside half the window counted from that key-up. Each line says which.
  • Half, because a quick double letter lifts and lands again 30 to 70 ms apart, while a switch that bounces as it opens is done in a few.
  • The repeat a held key makes by itself is never logged, and neither is text being composed by an input method.
  • Only the key position and the gap go into the log, and the log is gone when the tab closes.

Result

No repeats logged yet. Type slowly.

What this means

Repeats
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Presses
-
Window
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Held repeats ignored
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Next step Next: count how many keys register at once

All 20 checks

Typing passes that expose chatter 10

  • Busiest letters: E, T, A and O, 20 presses each In English text E is about 12.7 percent of all letters, T 9.1, A 8.2 and O 7.5. On a keyboard used for English these four switches have taken the most presses, so give each 20 slow ones.
  • Every letter five times, A to Z Press A five times with a clear pause between presses, then B, and on to Z: 130 presses. The pause keeps your own rhythm far outside the window, so every line in the log is worth a look.
  • Game keys: W, A, S, D and the arrows, 20 taps each Movement keys take short, hard taps for hours. Tap each 20 times the way you do in play, then 20 times slowly. The box holds the arrow keys while it has focus, so the page stays still. Click outside it to scroll again.
Show all 20 checks (17 more)

Typing passes that expose chatter, continued

  • Held key, five seconds Hold one key down and the system types it for you, at up to about 30 repeats a second on the fastest setting Windows documents. That is a 33 ms gap, inside a 40 ms window. The log should stay empty all the same: those repeats are flagged by the browser and no release comes between them.
  • Modifiers tapped alone, 10 presses each Shift, Ctrl and Alt, left and right, which the log tells apart (ShiftLeft, ShiftRight). A doubled modifier never shows as a doubled letter. It shows as a capital that fails to appear or a shortcut that misfires, which is why it goes unnoticed.
  • Normal typing, two minutes Write an email or some notes at your usual pace. This pass is for the key that only misbehaves in real use: warm, in the middle of a word, struck at an angle. Expect your own doubled letters to show if you type fast.
  • Number row and number pad, five presses each The log names the physical key, not the character. 7 and & are one key, Digit7, while the pad's 7 is a different one, Numpad7, and stays Numpad7 with Num Lock off. A repeat on one never hides in the other's count.
  • One suspect key, 100 slow presses A key that doubles once in 100 presses gets through a 30-press check clean about three times in four. One hundred presses catch it about 63 times in 100, and 300 presses about 95 times in 100. Rare faults need long runs.
  • Slow pangram, one key a second Type "Five dozen quick lambs jump over the grey wax hut" at about one key a second. It presses all 26 letters, and at that pace a second signal 12 ms after the first cannot have come from your finger.
  • Wide keys: Space, Enter, Backspace, both Shifts Long keys ride on a stabiliser bar and are often struck off centre. Press each 20 times in the middle, then 20 times at one end, and compare the counts. A key that repeats only at one end is telling you where, not just whether.

Setting your own window 4

  • 20 ms window for fast typists Logs only presses 20 ms apart or closer. Use it when normal typing at the default fills the log with your own doubled letters. The cost: a late second signal, 25 or 30 ms after the first, now goes unlogged.
  • 40 ms window (our default) A repeat is logged when the same key goes down, comes up and goes down again with less than 40 ms between the two presses. The figure is our starting choice and not a hardware standard. Change it to suit your hands.
  • 80 ms window for slow passes Widens the net for a switch whose extra signal arrives late. Keep to one press a second or slower with this setting, because a quick deliberate double tap can land inside 80 ms and would be logged as a repeat.
  • Your fastest double tap, 10 pairs Tap one key twice as fast as you can, ten times over. The page shows your smallest gap from press to press. Set the window a little under it and nothing you type on purpose can be logged as a repeat.

Log readings that need a second look 6

  • A held key that lets go by itself During the five-second hold the page saw a release and a fresh press that you did not make. In a game this is a character who stops walking for an instant. It suggests a contact that does not stay closed under a steady finger. Hold harder, then softer, and watch whether the count changes.
  • Doubled letters in documents, clean log here Three things to rule out. A held-key delay set very short (on Windows the shortest setting is about 250 ms) turns a lingering finger into repeats. A text-expansion or autocorrect tool may be doubling letters. Or the fault is rare, in which case run the 100-press pass on the letters that double.
  • Key names missing on a phone or tablet An on-screen keyboard has no switches to bounce, and some mobile browsers are documented as leaving the physical key code empty. The log then falls back to the character, so 7 and & show as two keys. Pair or plug in a hardware keyboard for a proper check.
  • One key repeats and every other key is clean The pattern points at that one switch and away from software. Dust and a worn contact are the usual suspects. Blow the key out with air, reseat the switch if your board is hot-swap, look for a debounce setting in the keyboard's own software, then run the 100-press pass again.
  • Repeats only when you type fast Words such as "letter" and "coffee" contain two real presses of one key, and quick fingers bring them close together. Measure your fastest double tap, set the window under it, and see whether the repeats vanish. If they do, they were yours.
  • Repeats spread across many keys Thirty switches rarely wear out together. Look at what sits between the keys and the page: a remapping or macro tool, a remote-desktop session, a wireless link with a weak battery. Try a second keyboard in the same browser. If that one logs repeats too, the keyboards are in the clear.

How this list was compiled: Table written for this page. The 40 ms window and the 20 ms and 80 ms alternatives are this site's own starting values and not a standard: no body publishes one, which is why the page lets you change it. The pangram was written for this page and checked to contain all 26 letters. The sums are computed: 1,000 ms divided by 30 repeats is 33 ms, and a key that doubles once in 100 presses gets through 30 presses clean with probability 0.99 to the power 30 (0.74), and is caught within 100 presses with probability 0.63 and within 300 with 0.95. That a held key sets the repeat flag on its key events is from https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/repeat, and browser support was read from api/KeyboardEvent.json in https://github.com/mdn/browser-compat-data (keys api.KeyboardEvent.repeat and api.KeyboardEvent.code, both checked 2026-09-19): repeat exists in Chrome from 32, Firefox from 28 and Safari from 10.1; the Chrome notes there say that before Chrome 137, with several keys held on Windows or Linux, a repeat of the most recently pressed key could carry the flag wrongly set to false, and that on Linux under X11 the same held until Chrome 139; and the physical key code is recorded as always empty in Chrome and Firefox on Android. That the code names a physical key and is not altered by the keyboard layout or which modifier keys are down is from https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/code (checked 2026-09-19). That Digit7 and Numpad7 are two separate code values is from the W3C Recommendation UI Events KeyboardEvent code Values of 22 April 2025 at https://www.w3.org/TR/uievents-code/ (checked 2026-09-19). That the pad key stays Numpad7 with Num Lock off is this page's inference from those two statements; neither page says it in those words. The held-key delay of about 250 ms to about 1 second and the repeat speed of about 2.5 to about 30 a second are the ranges Microsoft documents for Windows at https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-systemparametersinfoa, and the bounce setting of Filter Keys (the time that must pass once a key is released before a second press of the same key is accepted) is at https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-filterkeys (both checked 2026-09-19). That key contacts bounce several times before settling, that the keyboard's processor turns this into one confirmed keystroke, and that capacitive switches need no debouncing follow https://en.wikipedia.org/wiki/Keyboard_technology, and the share of E, T, A and O in English text follows https://en.wikipedia.org/wiki/Letter_frequency (both checked 2026-09-19). Licence: own work

How it works

One press, two letters: this keyboard double click test logs every key that fires twice inside a 40 ms window you can change, and counts them by key. A held key is ignored. On a phone, use a physical keyboard.

Read the full guide

Run the double key press test slowly

Chatter shows at low speed: press E once and two letters arrive 12 ms apart. Typed fast, the two Ts in "letter" are real presses that can land near the window. Begin with Slow pangram, one key a second. The result reads: 3 repeats arrived inside the 40 ms window on these keys: E 2, Space 1.

Why the keyboard double click tester skips held keys

Hold a key and the system types it for you, at gaps that can fall inside the window. That is no fault. Browsers flag those repeats, and no release comes between them. The log takes only a key that goes down, up and down again inside the window. Held key, five seconds proves it on your machine.

  • The Window field starts at 40 ms, our default. Type another number, or set it from your fastest double tap.
  • A key doubling once in 100 passes 30 presses three times in four. Run One suspect key, 100 slow presses.
  • The log names physical keys: 7 and & are both Digit7, and each Shift is counted apart.

Questions and answers

What is key chatter, and is this a keyboard chatter test?

Yes: chatter is one press that reaches the computer as two, which this log catches. Switch contacts bounce before they settle, and the keyboard's processor should smooth that into one keystroke, called debouncing. When a bounce outlasts the wait, "the" comes out as "thhe".

Does a logged repeat mean my keyboard is broken?

No. The log only says which keys repeated, how often and how closely. One key repeating while the rest stay clean points at that switch. Repeats across many keys point at software or a wireless link, so try a second keyboard.

Can I stop a key typing twice without replacing it?

Sometimes. Blow the key out, because dust under the cap can cause it. Some keyboards' software lets you lengthen the debounce time. Windows has a bounce option inside Filter Keys, which ignores a second press that follows a release too closely, fast doubled letters included.

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