iCloud & iCloud Photos · Universal Clipboard and Handoff
Does Junk Yard save things copied on my iPhone through Universal Clipboard?
Short answer: It can — Universal Clipboard places iPhone or iPad copies on your Mac's clipboard, where Junk Yard sees them like local copies. Turn off Handoff in System Settings → General → AirDrop & Handoff if you don't want that.
It can. Junk Yard keeps a history of what lands on your Mac's clipboard, and when Universal Clipboard pastes something from your iPhone or iPad onto the Mac's clipboard, it arrives there like anything you copied locally.
If you'd rather that didn't happen, turn off Handoff on the Mac in System Settings → General → AirDrop & Handoff, or switch off Capturing in the Junk Yard header while you work.
Scraps in Junk Yard clear themselves on the timer you choose, and Junk Yard runs on your Mac. See Junk Yard.