iMovie library on Mac: can you delete render files?

Where it is

What it is

iMovie keeps everything in one package, iMovie Library.imovielibrary in your Movies folder. It contains the video you imported, your projects, and render files.

Render files are preview versions iMovie creates while you edit, so that titles, effects and transitions play back smoothly. They are rebuilt from your clips whenever they are needed, which makes them the one part that can go without losing work.

The library grows mostly because imported footage is copied into it. A few long clips from a phone or camera take far more space than any render files.

How big it gets

Often tens of GB once you have imported footage. Render files are a smaller share of that, typically up to a few GB.

How to clear it by hand

1. Open iMovie, choose iMovie in the menu bar, then Settings.
2. Next to Render Files, click Delete, then confirm. This removes render files for all projects in the library.
3. For more space, export finished movies with File, Share, then delete projects and events you no longer need from inside iMovie. Deleting an event removes its footage from the library.
4. To keep everything but get it off the startup disk, quit iMovie and move iMovie Library.imovielibrary to an external drive, then open it from there by holding the Option key while starting iMovie.
5. Do not open the package in Finder and delete files inside it.

What happens afterwards

After deleting render files, iMovie creates them again as you play or edit a project, so previews may stutter briefly at first. Deleted projects and events cannot be recovered unless you have a backup.

How Diskzy handles it

Diskzy shows the size of the iMovie library on the disk map, and Search can find other large video files by kind and size. Deleting render files is done in iMovie.

Related guides

• Final Cut Pro render files(inside each Final Cut library)
• Photos Library~/Pictures/Photos Library.photoslibrary
• GarageBand sound library/Library/Application Support/GarageBand