Mac storage basics · Photos, music and video
How do I free space used by Final Cut Pro libraries?
Short answer: Choose File → Delete Generated Library Files to remove render, optimised and proxy media, which Final Cut can recreate. Finished libraries can be kept on an external drive and opened from there.
Final Cut Pro libraries hold render files, optimised and proxy media alongside your projects. Select a library in the sidebar and choose File → Delete Generated Library Files… to remove render files and, optionally, optimised and proxy media; Final Cut recreates them when needed.
Final Cut Pro can open libraries stored on an external drive, so finished libraries can be moved there whole — quit Final Cut first, copy the library in Finder, open the copy to check it, then delete the original. For other big folders, see moving folders.