The Universal Clipboard Conflict
Apple’s ecosystem relies heavily on “Continuity” features, one of which is the Universal Clipboard. This allows you to copy text on your iPhone and instantly paste it onto your Mac. However, to maintain synchronization across devices signed into the same iCloud account, macOS constantly monitors and sometimes aggressively manages the clipboard state. If you copy a complex item (like a high-res image or a large block of formatted code) on your Mac, and then simply wake up your iPhone in the same room, macOS might automatically clear or overwrite the Mac’s clipboard in an attempt to sync a newer, blank, or text-only state from the mobile device, causing you to lose what you just copied.
Disabling Handoff to Preserve Clipboard Integrity
To ensure your copied items remain exactly where you put them and to stop macOS from automatically clearing the clipboard due to sync conflicts, you must disable the Handoff feature on your Mac.
Click the Apple logo in the top-left corner and open System Settings. In the left-hand sidebar, click on General. In the General menu, locate and click on AirDrop & Handoff. Look for the toggle switch labeled Allow Handoff between this Mac and your iCloud devices. Click the toggle to turn it to the Off position.
By disabling Handoff, you completely sever the Universal Clipboard connection. Your Mac’s clipboard will now operate entirely locally and independently. While you lose the ability to copy-paste between your phone and computer, your Mac will never again automatically clear or overwrite your clipboard based on the proximity or status of your other Apple devices.