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A Final Cut library holds four things you can delete and one you cannot

Render files, proxies, optimised media and backups all regenerate. Telling them apart from your original footage is the whole job.

6 min read

A Final Cut Pro library looks like a single file and is a folder with a package flag. Inside it there is footage you cannot replace and several kinds of generated media that rebuild themselves, and the difference between them is the difference between a safe cleanup and losing a shoot.

What is inside a library

Inside the libraryRegeneratesTypical share
Render filesYes, on playbackOften the largest single part
Optimised media (ProRes copies)Yes, from the originalsVery large, several times the source
Proxy mediaYes, on demandLarge but much smaller than optimised
Thumbnail and waveform cachesYes, quicklySmall
Original media, if imported into the libraryNoWhatever your footage is

The single most important setting is in the import options: Leave files in place against Copy to library. The first keeps originals outside and makes the library disposable. The second makes the library the only copy of your footage, and everything below has to be done carefully.

Weigh it before touching it

# The library itself
du -sh ~/Movies/*.fcpbundle 2>/dev/null

# Inside one, largest parts first
du -sh ~/Movies/MyProject.fcpbundle/* 2>/dev/null | sort -h | tail -10

# Generated media specifically, across every library
find ~/Movies -type d \( -name "Render Files" -o -name "Transcoded Media" \) -prune \
  -exec du -sh {} \; 2>/dev/null | sort -h | tail

# Automatic backups, which live outside the library
du -sh ~/Movies/"Final Cut Backups.localized" 2>/dev/null

Deleting the generated media properly

  1. In Final Cut, select the library, then File, Delete Generated Library Files.
  2. Tick Delete Render Files, and choose All rather than unused if the project is finished.
  3. Tick Delete Optimized Media and Delete Proxy Media if the originals are safe elsewhere.
  4. Let Final Cut do it rather than deleting folders inside the package, so the library's own database stays consistent.

Doing this through the application matters more here than in most cleanups, because the library indexes what it contains. Removing files underneath it leaves entries pointing at media that is gone.

The backups folder nobody looks in

Final Cut keeps automatic backups of the library database in ~/Movies/Final Cut Backups.localized, one per save point. They are small compared with media and they accumulate for years. Deleting old ones is safe and does not touch the library itself.

Where the rest of a video machine goes

Camera originals outside the library, exports, and the caches of every other tool are usually a larger total than Final Cut. Video project files covers the footage, the DaVinci Resolve cache the equivalent in the other direction, and storage for video editors puts the whole workflow together.

Common questions

Can I delete Final Cut Pro render files?

Yes. Use File, Delete Generated Library Files inside Final Cut and choose Delete Render Files. They rebuild during playback, so the only cost is time.

What is taking up space in my Final Cut library?

Usually optimised media and render files rather than your footage. Optimised media is a ProRes copy of every clip and can be several times the size of the original.

Is it safe to delete media inside a .fcpbundle?

Not by hand. The library keeps its own index, so removing files underneath it leaves broken references. Use Final Cut's own Delete Generated Library Files, and never delete original media that was copied into the library.

What is the Final Cut Backups folder?

Automatic copies of the library database, kept in ~/Movies/Final Cut Backups.localized. They are small, they accumulate over years, and deleting old ones does not affect the library.

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