Quick answer
A working key turns green when you press it. A key that stays grey is not sending a signal, and a key that shows up twice in the log for one press is chattering (double-typing).
How to use the Keyboard Tester
- Click once anywhere on this page so your browser window has focus.
- Press every key on your keyboard, one at a time. Keys turn blue while held and stay green after they register.
- Any key that stays grey after pressing is not sending a signal. Press it a few more times, then check the cable, batteries or Bluetooth connection.
- To test ghosting, hold several keys at once and watch the Held now and Max held counters.
- Click Reset test to start again.
Example
Say your E key sometimes types twice. Press it slowly ten times while watching the key log under the keyboard. If one press creates two log entries, the switch is chattering, a common fault on worn mechanical switches. If the key never appears at all, it's dead or its connection is broken.
For gaming, hold W, A, Shift and Space together. If Max held reaches 4, your keyboard registers that combination. Many budget membrane keyboards top out at 2-3 keys in certain combinations. That limit is called ghosting or key blocking.
How it works
When you press a key, your keyboard sends a scan code to your computer and the browser turns it into a keyboard event with two values: key, the character typed (which depends on your language layout), and code, the physical position of the key (for example KeyZ). This tester uses the physical code, so it works the same with QWERTY, QWERTZ, AZERTY and other layouts.
Everything happens locally in your browser. Nothing you type is stored or sent anywhere.
A few keys can't be tested in a browser. Fn is handled inside the keyboard itself, and your operating system may capture keys like Print Screen, the Windows or Command key, or media keys before the page sees them.
Fixing the most common keyboard problems
- Only some keys fail on a laptop: if a whole row or block stops working at once, the ribbon cable or the keyboard controller is the likely cause, not the keys themselves.
- A key works only when pressed hard: dirt under the keycap. Turn the keyboard upside down and use short bursts of compressed air at an angle.
- Wireless keyboard misses keys: replace the batteries first, then move the USB receiver to a front port or an extension cable so it's closer to the keyboard.
- Wrong characters appear (for example Z and Y swapped): the keyboard is fine. Your operating system is set to a different layout, such as German QWERTZ instead of US QWERTY.
- Spilled a drink? Unplug it immediately and let it dry upside down for 24-48 hours before testing again.
Frequently asked questions
Why doesn't my Fn key light up?
The Fn key never sends a signal to the computer. The keyboard uses it internally to change what other keys do. To check it, hold Fn and press a function key: if that key's action changes, Fn works.
What is keyboard ghosting?
Ghosting, or key blocking, happens when a keyboard can't register certain combinations of keys pressed together. Hold several keys and check the Max held counter. Keyboards with N-key rollover register every key you hold.
One key types two letters. Is my keyboard broken?
That's usually key chatter: a worn or dirty switch makes contact twice in a single press. Cleaning the switch with compressed air often helps. On many mechanical keyboards the switch can be replaced.
Does this work with laptop and Bluetooth keyboards?
Yes. Any keyboard your computer recognizes works, including laptop, wireless and Bluetooth keyboards. On phones and tablets, an external keyboard works, but the on-screen keyboard doesn't send physical key codes.
Is anything I type recorded?
No. Key presses are only shown on this page and are cleared when you reload it. Nothing is saved or uploaded.