imovie project to flash drive

You cannot transfer the editable project itself to a USB flash drive. You can transfer the iMovie library that contains the project to a flash drive that is formatted Mac OS Extended (Journaled) or APFS. However, you can transfer the independent exported movie from iMovie. .

If the flash drive is formatted FAT 32, a windows format, the maximum size of any file can only be 4GB or less, no matter what the overall capacity of the drive itself. If that's the case, you need to back up your flash drive and then convert it to ExFat format (if you want it to be compatible with both Apple and Windows) or Mac OS Extended (Journaled) or APFS formats if you intend to use the drive only on Apple devices.

-- Rich

Rich, how about transporting the imovie library to an external HD to make space on my MacBook Pro?

elicia99,

Moving an iMovie library to an external HD is a good way to free up space on your Mac. The drive must be formatted Mac OS Extended (Journaled) or APFS. If you need to reformat the drive please note that reformatting erases all data on the drive, so you first need to back up any data that you want to keep.

— Rich