QuickDeviceTest Device test / Keyboard test
Keyboard test
Press any key. It lights up on the layout, its code appears below, and keys that never register stay dark. Works with laptop, mechanical and wireless keyboards.
Reading the readouts
- event.key: the character your layout produces (for example "z" on a US board, "y" on a German one for the same key).
- event.code: the physical key position, independent of layout. Useful for game key binding.
- keyCode / location: the legacy numeric code, and whether it was the left, right or numpad copy of a key.
- Held now / max rollover: how many keys are down right now, and the most seen together.
A key doesn't light up
- Check it in another app (a text editor) to rule out the browser.
- Wireless: replace the battery or recharge; low power causes missed keys first.
- Remove the keycap and clean underneath, or for mechanical boards, try a spare switch if it's hot-swappable.
- If keys fail only in combinations, run the ghosting test.
Questions
How do I test every key on my keyboard?
Click anywhere on this page, then press each key. Keys light yellow while held and stay green once they have registered. The counter shows how many keys of the standard layout have been seen; any key that never turns green is not reaching the computer.
Why don't the Fn or media keys show up?
Fn is handled inside the keyboard itself and never sends a key event, so no website can see it. Many media and brightness keys are also handled by the operating system before the browser receives them.
Some shortcuts like Ctrl+W close the tab. Why?
Browsers reserve a few shortcuts (close tab, new window, quit) and don't let pages block them. Test those keys individually instead.
What is key rollover?
The number of keys the keyboard can report at the same time. Hold several keys down and watch "max rollover". Many USB keyboards report 6 plus modifiers; gaming keyboards often report every key (N-key rollover).
A key types twice. Is it broken?
Repeated characters on a single press are "chatter", often caused by dust or a worn switch. Watch the key strip: one press should add one character. Try compressed air, or for mechanical boards, a switch cleaner.
Does it work for laptop keyboards and non-US layouts?
Yes. The picture shows a US layout, but keys are matched by their physical position (event.code), so a German or French keyboard lights the same physical keys. The event.key readout shows the character your layout actually produces.