Copy between Apple devices with Universal Clipboard

Universal Clipboard is one of those features that "just works" as long as it's set up on all your devices correctly. Here are the requirements needed to use this feature:

Sign into each device with an Apple ID:

Each device you want to work with a universal clipboard must be signed into the same iCloud account. Check these on your Mac by going to System Preferences > Apple ID and Settings > "Your Name" on your iPhone.

Bluetooth: Each device must have Bluetooth turned on.

Wi-Fi: Each device must be connected to the same Wi-Fi network.

Handoff: Each device must have Handoff enabled. On a Mac, you will find this under System Preferences > General:

On an iPhone or iPad you will find this in Settings > General > AirPlay & Handoff:

Generally speaking, this feature "just works" assuming your settings are correct. Keep in mind if you copy a large video or image file, it may take a minute or two to fully copy. Also, if you copy one item but don't paste it immediately on a different device, the clipboard on the device you are using may revert back to what was previously on it.