The Peripheral Tug-of-War
Apple’s Magic Keyboard and other Bluetooth peripherals are designed to seamlessly integrate with the macOS ecosystem. However, this seamlessness becomes a severe problem if you use the same Bluetooth keyboard with multiple Apple devices (such as an iMac in your office and a MacBook on your couch). When you wake up your MacBook and tap the keyboard, the iMac in the other room might detect the signal first and automatically connect to it. You are left typing on a dead keyboard, while your iMac silently registers every keystroke, forcing you to physically go to the other machine, turn off its Bluetooth, and manually repair the keyboard to your laptop.
Breaking the Automatic Pairing
To retain manual control over which device your peripherals talk to and stop macOS from automatically connecting to your Bluetooth keyboards when they are in range, you must explicitly tell the Mac to forget the device.
Click the Apple logo in the top-left corner and select System Settings. In the left-hand sidebar, click on Bluetooth. In the main panel, you will see a list of “My Devices” that are currently paired. Locate the specific keyboard (e.g., “John’s Magic Keyboard”) that keeps hijacking your connection. Hover your mouse over the keyboard’s name and click the small ‘i’ (info) icon that appears next to it. In the pop-up window, click the Forget This Device button. macOS will completely wipe the pairing profile from its memory. From now on, when you turn the keyboard on, that specific Mac will ignore it entirely, allowing your other Apple devices to connect without interference.