How do I fix an iMac 2021 keyboard that adds extra characters when typing?

Hi,

To fix an iMac 2021 Magic Keyboard that adds extra characters, check your input source layout, clean debris from the keys, or adjust your macOS key repeat settings.

Software and Settings Fixes

• Check Input Sources: Go to the Apple menu > System Settings > Keyboard, and look under Text Input to click Edit. Ensure only your correct language layout (like U.S. or British) is listed, and delete any incorrect or extra layouts.
• Adjust Key Repeat: If the keyboard is repeating letters or adding extra strings of the same character when pressed once, go to System Settings > Keyboard and adjust the sliders for Key repeat rate and Delay until repeat, or turn key repeat off to test.
• Toggle Accessibility Options: Go to System Settings > Accessibility > Keyboard, then turn Sticky Keys or Slow Keys on and off again to clear out any buggy software loops.
• Reset Bluetooth Connection: Turn off your Magic Keyboard using the switch on the back, wait a few seconds, turn it back on, and remove/re-pair the device via your Mac's Bluetooth settings.

Hardware Troubleshooting

• Clear Debris: Turn the keyboard upside down and gently shake it, or use a can of compressed air to spray around the affected keys to dislodge hidden dust or sticky residue causing keys to register double inputs.
• Test an Alternative Keyboard: Plug a wired USB keyboard or pair a different Bluetooth keyboard to your iMac. If the alternate keyboard types normally, your 2021 Magic Keyboard has a physical internal switch failure and must be replaced

Perhaps the keyboard is running on a weak battery? Connect the keyboard to the iMac to charge its internal battery. While connected to charge, it will also behave as a wired USB keyboard.

If the keyboard continues to misbehave, connect a different USB keyboard and see if the problem goes away. Maybe there is a hardware problem with your current keyboard?