What this keyboard tester does
A keyboard tester answers one simple question about every key you
own: does it still work? Press a key and the matching cap
on the on-screen keyboard lights up under your finger and stays
marked in green, with a small number in the corner counting its
presses. Sweep the whole board — letters, number row, punctuation,
Shift, Ctrl, Alt, Enter, the arrows — and two kinds of trouble
announce themselves. A key that never lights up is
not reaching your computer at all. A key whose counter jumps by two
or three on a single press has chatter — a worn switch
bouncing and registering twice, a classic first symptom of a dying
mechanical keyboard. The panel under the board also reports each
press the way a browser sees it: the key's name, its
event.key value, its physical event.code,
and the legacy event.keyCode number.
When is this useful? When a second-hand keyboard arrives and you want proof every switch fires before the return window closes. After a spill, to map exactly which keys the coffee reached. When a game or a work shortcut "stops working" and you need to know whether the key or the program gave up. And when a laptop key feels fine but produces nothing — the tester tells you in seconds whether you are shopping for a keyboard or just for a settings change.
How to run a complete test
- Go row by row, pressing each key once, firmly, the way you type. Green means received.
- Test both Shifts, both Ctrl/Alt keys if your board has them — they are separate keys with separate switches.
- Try key combinations afterwards: hold Shift and press a letter — the panel should show the capital letter as the key value while the same physical cap lights.
- Watch the counters. One press should always add one. Double counts mean chatter; a climbing counter while held is normal key repeat, not a fault.
- Function and media keys: many laptops send F1–F12 only with the Fn key held, and volume/brightness keys may be handled by the system before the browser. If the panel names them, they are being received even without a cap on the board.
If a key fails
First, rule out the cheap causes: try a different USB port, re-pair a wireless keyboard, and check for crumbs — a single crumb under a keycap kills a key more often than electronics do. On a mechanical keyboard, a failing switch can often be swapped; on a laptop or membrane board, a dead key usually means a replacement keyboard, though an external one is a perfectly good life-extension for an otherwise healthy laptop. If a whole row or column is dead, that is the keyboard's internal wiring, and no cleaning will fix it. And one boundary worth knowing: keys the operating system reserves — the Windows/Command key, some system shortcuts — may open menus instead of lighting up here. That is your system doing its job, not a fault, so test those in the system itself.
Frequently asked questions
How do I test whether a key is working?
Just press it. The matching key on the on-screen keyboard lights up while you hold it and stays marked in green afterwards, with a small counter showing how many times it has been pressed. Work through the whole board — letters, numbers, modifiers, arrows — and any key that never lights up is a key your computer is not receiving.
A key does not light up. Is the keyboard broken?
Not always — it means this page never received the key press. Some keys are captured by the operating system first (the Windows/Command key, some function keys, volume and brightness keys), and a few browser shortcuts are reserved. If an ordinary letter, number or punctuation key never lights up on any attempt, the switch under it is likely faulty or the keyboard has a dead row or column, which points to hardware.
What are 'key', 'code' and 'keyCode'?
They are three ways a browser describes a key press. 'Key' is the character or action produced (like 'a', 'A' or 'Enter') and changes with Shift and Caps Lock. 'Code' is the physical position on the keyboard (like 'KeyA'), which stays the same on any language layout. 'KeyCode' is the older number older websites used (65 for A). Programmers use these to build keyboard controls; this page shows all three for every press.
Why does the page capture Tab and the spacebar?
So the test can see them. Normally Tab moves you to the next link or button and the spacebar scrolls the page — either one would break the test before the press registered. While this page is open it holds those two keys (plus Backspace and the arrows) for testing instead. To leave the page while testing, use your mouse. Everything returns to normal the moment you close or leave this tab.
Is what I type recorded or sent anywhere?
No — and do not test that claim by typing a password. The tester only reacts to individual key presses inside this page, in your browser. No keystrokes are stored, uploaded or shared, and nothing is recorded once you leave the page. Still, as a habit, never type passwords into any test page, including this one.
Private by design: this tester reacts to key presses inside this page only. Nothing you press is recorded, uploaded or stored — and never type a password into any test page, this one included.