▮ Device Bench

Device test · Input

Spacebar Counter

Tap the spacebar and every real press is counted the moment your keyboard reports it — auto-repeat filtered out, presses per second computed live, and suspiciously fast double-registrations flagged as chatter. Everything runs locally in your browser; no keystroke leaves your device.

Presses0 ModeFree count Time0.0 s Rate0.0/s Chatter0

Press the spacebar — in a timed mode the clock starts on your first press.

How this test works

The counter listens for keydown events whose code property is Space — the physical spacebar, on any language layout. Every real press increments the total; auto-repeat events, which the operating system fabricates while a key is held, carry a repeat flag and are ignored. Alongside the raw count, the readout tracks elapsed or remaining time, the running presses-per-second rate, and the gap between each pair of consecutive presses.

Timing comes from the browser's monotonic clock (performance.now), which counts milliseconds independently of the wall clock. In timed modes the window opens on your first press rather than when you click a mode button, so reaction time never eats into the run; when the window closes the result is posted and later presses are ignored until you reset. The chatter check compares each keydown to the one before it: a gap under 30 milliseconds is beyond human finger speed for two separate presses, so it is flagged as a likely double-registration from the switch itself.

Browsers deliver key events with some timing jitter, so one chatter flag in a frantic run is not a verdict — repeated flags on single deliberate presses are the meaningful signal. The rate figure is only as precise as event delivery on your system, and nothing here can measure the switch's electrical behavior, actuation force, or feel. If the chatter counter keeps climbing, the keyboard chatter guide covers cleaning, debounce settings, and when a switch is worth replacing.

Frequently asked questions

Why did the chatter counter go up when I only pressed once?
Two registrations under 30 milliseconds apart are faster than a human can complete two separate presses, so the counter flags them as likely switch chatter. A single flag can be timing noise from the browser, especially on a busy system. If the counter climbs on ordinary deliberate presses, the switch under your spacebar is probably double-registering and needs cleaning or replacement.
Does holding the spacebar down add to the count?
No. When you hold a key, the operating system generates auto-repeat events, and the counter drops every event marked as a repeat. Only the initial contact of each physical press is counted, so holding the bar for ten seconds still counts as one press.
What is a good presses-per-second score?
There is no official benchmark. Most people land somewhere around 6 to 9 presses per second with one thumb over a short burst, and rates drop as the run gets longer because fatigue sets in fast. Technique matters more than hardware: alternating two fingers or drumming can roughly double a single-thumb rate. Treat the number as a way to compare your own runs, not other people's.
Why doesn't the page scroll when I press the spacebar?
Browsers normally treat the spacebar as page-down. This tool intercepts that so a fast run doesn't send you flying down the page. Buttons and links still respond normally when they have keyboard focus — pressing Space on a focused button activates it instead of adding to the count.
Can this tool prove my spacebar is faulty?
It can show strong evidence, not proof. What it sees is the stream of key events the browser delivers, after the keyboard controller, the operating system, and the browser have each handled them. Repeated chatter flags on slow, deliberate presses point clearly at the hardware; an occasional flag during very fast mashing may just be timing jitter. For a definitive answer, test the same keyboard on a second computer.

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