Preparation before the test
Symbol-key positions differ between JIS and US layouts. Choose the 100%, 75%, or 60% layout closest to your keyboard, then test with minimal interference from the IME or keyboard shortcuts.
- If it is wired, check another port, or if it is wireless, check the remaining battery level.
- Temporarily pause any background key-remapping software and compare the results
- On a laptop, compare the built-in keyboard with an external keyboard
Confirmation procedure
- Press every letter key once and notice that the keys you press are colored on the screen.
- Press Shift, Ctrl, Alt and a letter key at the same time to see if multiple keys are detected at the same time.
- Press the suspicious key at regular intervals and check whether multiple events occur for a single operation.
- Check whether the CapsLock status display matches the actual input status.
Troubleshooting by Symptom
| Symptom | Possible cause |
|---|---|
| Double input only for specific keys | Worn, dirty, or bad contacts on the switch |
| Multiple keys are unstable at the same time | USB, wireless, power, driver |
| Occurs only in specific apps | App shortcuts and input settings |
| Repeated input occurs only while a key is held down | OS key repeat settings |
The browser displays keyboard events reported by the operating system. This alone cannot confirm a hardware fault, so compare the results on another device or USB port.
Try It in Your Browser
Your input is processed entirely in your browser. Keep the original data, review the output, and only then save or share it.
Open the Keyboard Tester