KeyboardTest is a free, single-purpose tool: a full-size on-screen keyboard that lights each key as you press it. It’s built for anyone diagnosing a keyboard — a gamer checking rollover before a tournament, a buyer testing a second-hand board, a laptop owner whose E key just died, or a developer who needs the exact code/key/keyCode triple a keystroke produces.

What the tester shows

• Per-key state — green while held, tinted with a dot once tested, amber when a key is held long enough to look stuck.
• The raw event — event.code, event.key, event.keyCode, event.which and event location for every keystroke, the same values a developer would read in DevTools.
• Rollover counters — live held-count and the maximum simultaneous presses your board managed, plus a held-keys strip so you can see exactly which of your pressed keys were reported.
• A press history — the last 40 key events as chips, so a key that flickers in and out leaves a trail.
• ANSI and ISO layouts — including the L-shaped ISO Enter and the extra <> key beside left Shift.

How the detection works

Everything runs in your browser. The page listens for the standard keydown/keyup events the OS delivers and maps each event.code to a keycap — that’s why it can show the physical key position regardless of what character your layout prints. Nothing is sent anywhere: there is no backend, no account, and your key presses are never logged by us.

One deliberate design choice: the tester only intercepts keys that would otherwise scroll the page or open browser UI — F-keys, arrows, Tab, Space — and only while the tester is focused or your pointer is over it. Ctrl/⌘ shortcuts always pass through.

Who maintains it

KeyboardTest is maintained by the Tolerence team: small, independent, and building focused utility sites. Scripted keystrokes drive the site’s automated test, which requires a 104-key ANSI layout (105 on ISO), auto-repeat that never inflates the press count, and F5 intercepted only while the tester has focus, never Ctrl combinations. AI coding and writing assistants helped produce the detection script and the guides, under the direction of the site’s operators. Found a key that behaves strangely, a layout we should add, or a bug in the detection? Contact us — hardware-quirk reports get answered first.