Open the keyboard tester and press the suspect keys. Three patterns:
| What you see | Likely cause |
|---|---|
| Key registers in the tester but not in your app | Software: layout, shortcut, app setting (steps 1–4) |
| Key registers only when pressed hard or twice | Debris under the key or a worn switch (step 6) |
| A whole row, column or diagonal of keys never registers | Keyboard matrix / ribbon cable fault — hardware (step 8) |
- Fn lock. If F1–F12 do media things instead of F-functions (or vice versa), press Fn+Esc or Fn+Caps/Fn+F11 depending on the laptop. Many gaming keyboards also have a “game mode” that disables the Windows key — look for a key with a joystick or lock icon (Fn+Win).
- Num Lock. The number pad types nothing or moves the cursor when Num Lock is off. On compact laptops the pad is overlaid on letters (U I O J K L M) and only active with Num Lock on — a classic “my letters type numbers” cause.
- Filter Keys / Sticky Keys (Windows), Slow Keys (Mac). Windows: Settings › Accessibility › Keyboard › turn off Filter Keys and Sticky Keys (holding Shift 8 seconds switches Filter Keys on by accident). macOS: Accessibility › Keyboard › Slow Keys off. Also check Mouse Keys is off — it turns the keypad into mouse control.
- Wrong layout or language. If @ and “ are swapped, or keys type other letters, the layout changed: Windows Win+Space cycles layouts; macOS the input menu in the menu bar. Remove layouts you don’t use.
- Modifier remaps. macOS › Keyboard › Keyboard Shortcuts › Modifier Keys; Windows apps like PowerToys Keyboard Manager, AutoHotkey or gaming software can remap keys silently. Disable them to test.
- Dirt or a sticky switch. Power off, hold the keyboard at an angle and blast compressed air around the key. On mechanical boards pull the keycap (puller) and clean the switch; a drop of isopropyl alcohol on a swab around the stem can free a sticky one. Spilled drinks: unplug immediately, flip upside down, dry 48 h.
- Wireless and USB. Replace batteries; re-pair Bluetooth (forget + pair again); for USB try another port directly on the computer, not a hub. Some keyboards need their own software for extra keys.
- Driver and firmware. Windows: Device Manager › Keyboards › Uninstall device, restart. Gaming keyboards: update firmware in the maker’s app. Laptops: the maker’s support page for a keyboard/hotkey driver (Fn keys often live there).
- Tell hardware from software for certain. Restart and enter BIOS/UEFI (F2/Del at boot) and try the key there, or boot a live USB. If the key fails in BIOS, it is hardware. Laptop keyboards are replaceable parts; a dead row usually means the ribbon cable or the membrane.
Did it work?
Run the keyboard test again. If the device now registers here, every app that has permission will see it too.
Questions, answered
My letters type numbers.
Num Lock is on and your compact keyboard overlays a number pad on the letters. Press Fn+Num Lock (or Fn+F11 on many laptops).
The keyboard works in the tester but not in one game.
The game uses raw input or a different layout; check its control settings, run it as administrator once, and disable overlays (Discord, GeForce Experience) which can swallow keys.
Keys work, but repeat or double-type.
Dirt or a worn switch (step 6), or Filter Keys settings. On mechanical boards it is “chatter” — firmware updates or a switch swap fix it.