That one school project you edited in iMovie is still eating 30 GB

Updated September 2026 · 7 min read

iMovie is free, easy to use, and shockingly hungry for disk space. A single library with a few projects can easily reach 20–50 GB — even if the final exported video was only 2 GB. Here's why, and what you can safely do about it.

Why iMovie uses so much space

iMovie stores three kinds of files for every project:

• Original media. When you import a video clip into iMovie, it copies the full file into the library. Your original in Downloads or Photos stays, and now there's a second copy inside iMovie.
• Render files. iMovie pre-renders effects, transitions, and thumbnails so playback is smooth. These render files can be as large as the original footage — or larger if you have many effects.
• Exported movies. If you shared a project to a file, that exported video also lives inside the library.

Where iMovie libraries live

The default location is ~/Movies/iMovie Library.imovielibrary. Like Photos, it's a package file. You can right-click and Show Package Contents, but don't rearrange anything inside — the internal structure is linked to iMovie's database.

Some people create multiple libraries over the years. Check your ~/Movies folder — there may be old libraries from projects long finished.

Freeing space: the safe approach

1. Delete render files (biggest quick win)

Render files are regenerated automatically when you open a project. Deleting them is safe and often frees 30–50% of the library size:

1. Open iMovie.
2. Go to iMovie → Settings (or Preferences).
3. Click Delete Render Files.

Choose to delete render files for all projects, or only those older than a certain period. iMovie will re-render when you next open a project — it takes time but costs nothing.

2. Delete finished projects you no longer need

If you're done with a project and have already exported the final video, you can delete the project from iMovie. This removes the project's clips, edits, and render files from the library.

3. Move old libraries to an external drive

If you have finished libraries you might revisit someday, move them to an external drive instead of deleting:

1. Quit iMovie.
2. In Finder, drag the .imovielibrary file to your external drive.
3. Once copied, delete the local version.

To reopen later, double-click the library on the external drive. iMovie opens it directly from there.

4. Remove iMovie entirely if you don't use it

If you never edit video, uninstalling iMovie frees about 3 GB for the app itself. But the real savings come from deleting the library in ~/Movies. Just make sure you don't have footage in there you care about.

What not to do

• Don't delete individual files inside the library package. The database will lose track of them and the library may corrupt.
• Don't assume the exported video is the only thing that matters. Some people keep raw footage in iMovie as their only copy — check before deleting.

iMovie libraries are one of the less obvious storage hogs. For a broader picture of what fills your Mac, check our guide to finding large files.

FAQ

Is it safe to delete iMovie render files?

Yes. Render files are temporary pre-computed previews. iMovie regenerates them automatically when you open a project. Deleting them is the fastest way to reclaim iMovie space without losing any footage or edits.

Can I move my iMovie library to an external drive?

Yes — quit iMovie, drag the library file to your external drive, then open it from there. iMovie works fine with libraries on external drives, though performance depends on the drive's speed.

Why is my iMovie library bigger than my exported video?

The library contains all imported source footage (often much more than what ended up in the timeline), plus render files and thumbnails. The exported video is a compressed final product — the raw materials behind it are always larger.