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The iMovie library keeps a full copy of every clip, even after the movie is done

iMovie copies each clip into its library and adds render files on top. How to measure the library, clear what is safe, and move it off your Mac.

5 min read

You made a five minute video of a holiday, exported it, and shared it. The finished movie is about 1 GB. The iMovie library behind it is 40 GB, and it is still on your Mac a year later.

Why the library gets so big

  • Every clip is copied in. When you import from Photos, a phone or a folder, iMovie keeps its own copy inside the library. The original is still wherever it was, so the same footage is now on the disk twice.
  • Phone video is large. One minute of 4K at 60 frames a second from a recent iPhone is roughly 400 MB. Twenty minutes of raw clips is already 8 GB.
  • Render files. iMovie builds preview files while you edit, and they can add a large share on top of the clips.
  • Nothing is removed when you finish. Exporting a movie does not clean up the project. The library stays until you delete it.

Measure it

The library is a single file in Finder, but it is a folder underneath:

du -sh ~/Movies/*.imovielibrary

# What is inside, largest last
du -sh ~/Movies/iMovie\ Library.imovielibrary/* 2>/dev/null | sort -h | tail

If Terminal says it cannot read the folder, give it Full Disk Access in System Settings, under Privacy and Security, or right-click the library in Finder and choose Get Info.

What to clear, safest first

WhatWhat you loseHow
Render filesNothing, iMovie rebuilds them if needediMovie, Settings, Render files: Delete
Finished projects you exportedThe ability to edit that movie againDelete the project and its event in iMovie
The whole libraryEvery project in itQuit iMovie, move the library to the Trash
Old libraries you forgotNothing, if you never open themSearch Finder for .imovielibrary

Before deleting a project, check the exported movie plays and is saved somewhere outside the library, such as Movies or Photos. That exported file is your finished video; the library is only the workshop.

# Every iMovie library on your Mac, with sizes
mdfind 'kMDItemFSName == "*.imovielibrary"' | while read -r f; do du -sh "$f"; done

Keeping a project without keeping it on the Mac

If you might edit a movie again, move its library to an external drive instead of deleting it. Quit iMovie, drag the library to the drive, and open it from there by double-clicking. Once it opens correctly from the drive, move the copy on your Mac to the Trash. Moving files to an external drive covers which drive formats work.

Deleting the iMovie app itself

iMovie is a free App Store app and can be deleted from Applications and downloaded again later. Deleting the app does not delete your library, which is usually far larger. See iWork apps taking up space for the other free Apple apps, and video projects taking up space if you also use Final Cut Pro or other editors.

Common questions

Where is the iMovie library on a Mac?

By default it is in the Movies folder in your home folder, named iMovie Library. Finder shows it as a single file, but it holds every clip, project and render file inside it.

Is it safe to delete iMovie render files?

Yes. Render files are previews iMovie builds while you edit, and it makes them again if it needs them. Delete them from iMovie's settings rather than by hand.

If I delete the iMovie library, will I lose my exported movies?

No, as long as the exported file was saved outside the library, such as to the Movies folder or to Photos. You will lose the ability to edit those projects again.

Why is my iMovie library bigger than my videos?

iMovie copies each imported clip into the library and adds render files on top, so the library usually holds all of the raw footage plus previews, not just the finished movie.

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