I built a free keyboard testing toolkit - 6 tools, no install, and the keydown event is weirder than you'd think

Roach — Mon, 13 Jul 2026 11:06:46 +0000

What it is: fullkeyboardtest.com - a free, browser-based keyboard testing toolkit. It started as a simple "press a key, watch it light up" tester and grew into six tools:

Keyboard tester - every key highlights as you press it, with a progress bar of tested keys
Anti-ghosting / NKRO test - how many simultaneous presses your keyboard actually registers
Polling rate test - estimates your keyboard's report frequency in Hz
Typing speed test - WPM and accuracy
Event logger - raw key, code, and keyCode values for every event
Shortcut/combo tester - verify combos like Ctrl+Shift actually register
Everything runs entirely in the browser - no install, no drivers, no data leaves your device.

Why I built it: [your real reason - e.g. "I was buying a second-hand mechanical keyboard and wanted a fast way to check every key before paying."]

What I learned building it: the browser's KeyboardEvent API looks trivial until you hit the edge cases:

key tells you the character produced, code tells you the physical key - you need both, because layouts (QWERTZ, AZERTY…) remap characters but not positions.
Some keys never reach the browser at all (Fn is handled in the keyboard's own firmware).
Browsers reserve shortcuts like Ctrl+W - preventDefault handling has to be careful or testing modifier combos closes your tab.
Measuring polling rate from JS means fighting event-loop timing noise, so it's an estimate, not a hardware-level measurement.
Keyboards come in many physical layouts (full-size, TKL, 75%, 65%, 60%), so the on-screen keyboard can't be one fixed image.
Also on the site: guides on stuck keys and key chatter, a keyboard glossary, and the UI is translated into 10+ languages.

DEV Community: Roach

I built a free keyboard testing toolkit - 6 tools, no install, and the keydown event is weirder than you'd think