How Does Final Cut Pro Identify Matching Clips?
Internally, each master clip in a project has a unique number called a universally unique
identifier (UUID). No two clips in a project can have the same UUID. When you drag or
paste a clip from one project to another, the destination project may already contain a
clip with the same UUID as the source project clip. When the source and destination
clips have matching UUIDs, Final Cut Pro detects a match. When both clips’ properties
match, the clips match exactly. When the source and destination clips have one or
more nonmatching properties, you must choose how to resolve the differences.