Help · Mac storage

iMovie library too big?

By Grant and Brad, who make Pangalin's apps · Updated 11 October 2026

An iMovie library holds everything you've imported, plus render files iMovie makes to play edits smoothly. It grows quickly with video. You can shrink it from inside iMovie, or move the whole library to an external drive.

1. Delete render files

1. Open iMovie and choose iMovie › Settings (⌘,).
2. Next to Render Files, click Delete.

Apple says this removes render files from open libraries and no imported media. iMovie makes them again when needed; avoid doing it during an export, which would slow it down.

2. Remove media you don't need

The space is held by imported clips in your events, so deleting a project alone may not free much. Inside iMovie, delete clips or whole events you no longer need, for finished projects you've exported. Back up anything you might want to edit again.

3. Move the library to an external drive

Use an APFS or Mac OS Extended (Journaled) drive, not your Time Machine drive, an SD card, a USB stick or network storage. Back up first.

1. Quit iMovie.
2. In Finder choose Go › Home, open Movies and drag iMovie Library to the drive.
3. Double-click the copy on the drive to check it opens in iMovie.
4. Move the original to the Trash and empty it. This is permanent, so check the copy first.

Connect the drive before opening iMovie; if iMovie can't find the library, it starts a new empty one.

Using Final Cut Pro too? See Final Cut library too big.