Keyboard Tester

What a keyboard test actually tells you

A key that does nothing is easy to spot. The failures worth testing for are the ones you would otherwise blame on yourself: a key that registers twice from one press, a key that sticks down, or a keyboard that quietly drops inputs when several keys are held together.

This tool shows all three. Press a key and it lights up; let go and it unlights. A key that stays lit after you release it is stuck. A key that never lights is dead, disconnected, or being intercepted by software before the browser sees it.

What the numbers mean

Each press reports three different identifiers, and the difference between them matters:

• code — the physical key's position, such as KeyA. It does not change with your keyboard layout. On a French AZERTY keyboard the key where A sits on a QWERTY board still reports KeyQ.
• key — the character produced, which does depend on layout and on modifiers. Shift+1 gives !.
• keyCode — a legacy number, formally deprecated but still widely used. Included because older software and guides refer to it.

If a game or application is not responding to a key, comparing these three is usually how you find out why.

Rollover and ghosting

The counter showing how many keys are held at once is testing your keyboard's rollover. Cheap membrane keyboards share wiring between key groups, so holding three or four keys in certain combinations makes further presses vanish — or produce a key you never touched, which is called ghosting.

Hold W, A and Shift together, then try pressing Space. On a keyboard with full n-key rollover every one registers. On a basic membrane board, one of them will not. This matters mainly for gaming, where movement, sprint and jump are often pressed simultaneously.

How to use it

1. Click into the page first so the keyboard events reach it.
2. Press every key in turn. Each one turns coloured and stays marked, so you can see at a glance what you have covered.
3. Watch the untested list below the board. It names what you have not yet pressed.
4. Release each key and check it unlights. A key that stays lit is stuck.
5. Hold several keys at once to check rollover. The counter shows how many the keyboard is reporting together.
6. Start over to clear everything and test again.

Common uses and tips

Why people end up here

• Buying second-hand. The fastest way to check every key on a used keyboard or laptop before paying for it.
• After a spill. Liquid damage often kills a cluster of neighbouring keys rather than random ones, which this makes obvious.
• Chattering switches. A worn mechanical switch sends two presses from one push. The event log below the board shows each down and up, so a doubled press is visible.
• Diagnosing a game, where a key works in a text box but not in the game — usually a rollover limit or a remap.
• Checking a repair after replacing a switch or a keycap.

If a key does not register

• Try another application. If it fails everywhere, the problem is the keyboard or its driver. If it only fails in one place, something is intercepting it.
• Check for a function lock. Many laptops swap the F-keys for brightness and volume until you press Fn+Esc or a similar combination.
• Look for software remaps. Gaming software, accessibility tools and keyboard managers can all silently reassign keys.
• Some keys never reach the browser. The operating system claims a few for itself — the Windows key alone, print screen on some systems, and media keys. These may not register here even on a perfectly good keyboard.

Reading the event log

Every press produces a down and a up. Two downs with no up between them means a chattering switch or a stuck key. Holding a key produces repeated downs, which is normal auto-repeat, and only one up when you finally release.

What this tool can and cannot see

Everything here runs in your browser. Nothing about your keyboard, mouse or keystrokes is sent anywhere, stored, or logged — the page has no server to send it to.

What the browser gives a web page is also limited by design. It can see that a key was pressed and which one, but not what kind of switch it uses, its firmware, or anything about the device beyond what the operating system reports. A web page cannot tell a mechanical keyboard from a membrane one.

Questions people ask

Why does a key not light up?

Either the keyboard is not sending it, or something is intercepting it before the browser. Try the same key in a text editor to tell the two apart. A few keys — the Windows key on its own, some media keys — are claimed by the operating system and never reach a web page.

What is key rollover?

How many keys your keyboard can report pressed at the same time. Cheap membrane keyboards share wiring and drop inputs past three or four simultaneous keys; boards with n-key rollover report all of them.

What is ghosting?

When holding certain key combinations produces a key you never pressed. It comes from the same shared wiring that causes rollover limits.

My key registers twice from one press. What is that?

A chattering switch — the contacts bounce as they close. It is a common failure in worn mechanical switches and usually means the switch needs replacing.

What is the difference between code and key?

code is the physical position and never changes with layout. key is the character produced, which changes with layout and with Shift.

Is anything I type recorded?

No. The page runs entirely in your browser and has no server to send anything to.