How do I know if it's the keyboard or a software problem?

Test it on this page and on another computer. If the keys fail everywhere, it's the keyboard. If they work elsewhere, check the layout, drivers and accessibility settings.

Why does my keyboard type two letters when I press once?

That's key chatter from a worn or dirty switch. Cleaning can help; otherwise the switch or keyboard needs replacing. The tester highlights chattering keys.

Why is my laptop typing numbers instead of letters?

Num Lock is on for the laptop's built-in number pad. Turn Num Lock off, often with Fn plus a function key.

Keyboard keys not working? How to test and fix them

When a few keys stop working, the cause is usually dirt or a worn switch, a software setting, or the wrong keyboard layout. A quick test tells you which.

Open Keyboard Tester

1. Test every key

Open the keyboard tester and press each key. Keys that never light up aren't reaching the computer — a hardware or connection problem. Keys that light up but type the wrong character point to a layout setting. Keys flagged for chatter are registering twice.

2. Fix keys that don't register

Turn the keyboard upside down and tap it gently, or use short bursts of compressed air under the keys.
For a sticky key after a spill, unplug the keyboard (or shut down the laptop) before cleaning with a little isopropyl alcohol on a cotton swab.
External keyboards: try another USB port or cable, replace the batteries, or pair the Bluetooth connection again.
If a whole group of neighboring keys fails together, the internal cable or circuit is likely damaged — that's a repair job.

3. Keys type the wrong characters

Windows: Settings → Time & language → Language & region — check the keyboard layout matches your keyboard (for example US versus UK).
macOS: System Settings → Keyboard → Text Input — remove input sources you don't use.
Laptops: Num Lock can turn letters such as U, I and O into numbers on some models — turn Num Lock off.
Make sure Caps Lock or Fn Lock isn't switched on.

4. Keys lag, repeat or need a long press

Windows: turn off Filter Keys and Sticky Keys in Settings → Accessibility → Keyboard.
macOS: turn off Slow Keys in System Settings → Accessibility → Keyboard.
Windows: update or reinstall the keyboard driver in Device Manager.
A key that types twice on a single press has a worn switch — replace the switch or the keyboard.

Tools used in this guide

Keyboard TesterPress every key and see which ones work Mouse TestTest mouse buttons, double-clicks and scrolling Dead Pixel TestFind dead and stuck pixels on any screen