The fastest way to check every key
Click the keyboard on this page and press each key once, row by row, including function keys, arrows, the navigation block and the numpad. Every key lights up while you hold it and stays marked afterwards, and the Keys tested counter goes up. When you are done, any key that is still unmarked did not reach the browser.
Then check the three things a quick typing test misses: keys that stay lit after release (sticking), keys that appear twice in Last keys after a single press (chattering), and combinations that drop keys when held together (ghosting). Reset clears everything for a second round.
Try it here: Keyboard Test
Open the full tool pageReading the results
The panel also shows the key name, its code and whether it was the left or right version of a key like Shift or Ctrl. The code is based on the physical position, so the test works with US, UK, German, French, Turkish and any other layout. In Chrome and Edge the keys are even labeled with the letters of your own layout.
| What you see | Likely cause | First thing to try |
|---|---|---|
| A key never lights up | Dead switch, dirt under the key, damaged membrane or a key blocked by the system | Test the key in another app, then clean under it |
| A key stays lit after release | Sticky keycap or a switch that does not return | Clean the switch area; check for spilled liquid |
| One press shows two entries in Last keys | Chattering: a worn or dirty switch bounces | Compressed air, then switch replacement or repair |
| Some keys drop when you hold several | Ghosting or a rollover limit | Normal on many office keyboards; check the combination you need |
| Wrong letter appears on a key | Operating system layout does not match the keyboard | Change the input language or layout in system settings |
Stuck and chattering keys
A stuck key keeps sending its signal after you let go, or the keycap physically stays down. Sugar from a drink is the classic cause: it leaves a sticky film that slows the key. Crumbs and hair under a key cause the opposite problem, a key that needs extra force or does not register at all.
Chattering, also called double typing, is when one press produces two or more characters. Every mechanical switch bounces for a few milliseconds when its contacts close, and the keyboard ignores that with a short delay called debounce. A worn, oxidized or dirty switch bounces longer than the delay, so a single press is counted twice. It usually starts with the most used keys: space, E, A, Backspace. In the test, press the suspect key slowly 20 times and count the entries in Last keys; if 21 or more appear, it chatters.
Ghosting and key rollover explained
Most keyboards connect the keys in a grid of rows and columns instead of wiring each key separately. When three keys at the corners of a rectangle in that grid are held, the controller can see a fourth key that was never pressed. That phantom is ghosting. To avoid it, cheaper keyboards block the extra key instead, which is why some combinations simply drop a key. Gaming keyboards add a diode per key so every combination is read correctly.
Key rollover is the number of keys that register together. 2KRO means two keys are always safe; 6KRO is the classic USB limit of six keys plus modifiers; NKRO (n-key rollover) means every key at once. Hold the combinations you actually use, such as W, A, Shift and Space for games or Ctrl, Shift, Alt and a letter for shortcuts, and read Most at once. If it stays below the number of keys you are holding, that combination will fail in practice. Laptop keyboards and office keyboards commonly manage 2 to 4 keys in some combinations, which is fine for typing but limiting for games.
Keys a browser cannot see
Some keys are handled by the operating system or by the keyboard itself before a web page receives anything, so an unmarked key is not always broken. Fn is processed inside most keyboards and never sent to the computer. Media keys, brightness and volume keys often go straight to the system. The Windows key, Print Screen and some Ctrl or Alt combinations may be captured by the system too.
To check one of those keys, see whether it does its normal job: volume changes, a screenshot is taken, the Start menu opens. Esc is used by the test to leave the test area, so the rest of the page stays usable with the keyboard; click the keyboard again to continue.
Quick fixes before replacing a keyboard
- Restart and reconnect: unplug a USB keyboard and use another port; for wireless, replace the batteries and re-pair Bluetooth.
- Check system features: Filter Keys in Windows ignores brief or repeated presses and can make a keyboard feel dead; Sticky Keys turns on after pressing Shift five times.
- Check Num Lock and Fn Lock: with Num Lock off, the numpad works as arrows; with Fn Lock on, F1 to F12 act as media keys.
- Check the layout: if Z and Y or symbols are swapped, the system layout is wrong, not the keyboard.
- Clean it: unplug or power off, turn the keyboard upside down and tap it, then use compressed air at an angle. On mechanical keyboards remove the keycap with a keycap puller first.
- After a spill: disconnect power at once, turn it upside down, and let it dry for at least a day. For sugary drinks, clean with isopropyl alcohol; on a laptop, get service rather than opening it yourself.
- Replace the switch: on hot swappable mechanical keyboards a chattering switch can be swapped in a minute. Some vendors also offer firmware with a longer debounce time.
When to test a keyboard
Run the test when you buy a used laptop or keyboard, before the end of a return period for a new one, after a spill or cleaning, and when a game misses inputs. It takes about two minutes for a full size keyboard and needs no software, which also makes it handy on work computers where you cannot install anything.