To delete old iMovie projects and reclaim space, drag the iMovie Library.imovielibrary file from ~/Movies to the Trash if you're finished with everything — or, to keep your projects, delete the render files from iMovie settings or move the whole library to an external drive. iMovie stores every imported clip and render inside one big package; a few old projects can easily take 50–100 GB.

TL;DR

  • Done with all projects: trash iMovie Library.imovielibrary in Finder › Movies; iMovie rebuilds an empty library on next launch.
  • Keep projects, cut the bloat: iMovie > Settings > Render Files > Delete (render files regenerate automatically and safely).
  • Out of internal space but need the projects: drag the library onto an external drive and reopen it from there.
  • Render files are the heaviest, most disposable part of an iMovie library.
  • Deleting the library does not affect anything else on your Mac.

Where does iMovie store its files?

iMovie keeps everything inside a single package called iMovie Library.imovielibrary, located in your home folder under ~/Movies (the Movies folder in Finder's sidebar). That one file holds every project, every imported clip, and every render file iMovie has generated. Because imported 4K clips and renders are large, the library quietly balloons — a handful of old vacation or YouTube projects can occupy 50–100 GB. macOS often files this under "System Data" or "Other" in the storage bar, which is why the space can feel like it vanished.

How do I delete the entire iMovie library?

If you've already exported every video you care about, removing the whole library is the fastest way to reclaim the space:

  1. open Finder
  2. click Movies in the sidebar (or press Command + Shift + H, then open Movies)
  3. find iMovie Library.imovielibrary (the purple star icon)
  4. right-click and choose Get Info to confirm its size first
  5. drag the file to the Trash, then empty the Trash

The next time you launch iMovie it creates a fresh, empty library. Nothing else on your Mac is touched.

How do I free up space without deleting my projects?

If you still need the projects, you have two safe options.

Delete render files. Render files are the temporary previews iMovie creates while editing — the heaviest chunk inside the library, and fully disposable because iMovie rebuilds them on demand.

  1. open iMovie
  2. click iMovie > Settings in the menu bar
  3. next to Render Files, click Delete

Consolidate to an external drive. If the internal drive is full but the projects must stay live:

  1. plug in an external drive (formatted APFS or Mac OS Extended)
  2. in Finder, drag the .imovielibrary file onto the external drive
  3. double-click it from the external drive so iMovie reopens it from the new location

From then on iMovie reads and writes directly on the external drive, freeing your internal storage.

Is deleting iMovie render files safe?

Yes. Deleting render files is safe and reversible in practice — they are only cached previews, and iMovie automatically regenerates them the next time you open a project, with no loss to your edits or source clips. Trashing the entire library, by contrast, is permanent: it removes every project and imported clip inside it, so only do that after you've exported the finished videos you want to keep. When in doubt, delete render files first and see how much that recovers.

FAQ

Why is my iMovie library so large?

An iMovie library is large because it stores every imported clip plus the render (preview) files iMovie generates for each project, all inside one .imovielibrary package. A few projects with 4K footage can reach 50–100 GB.

Does deleting iMovie render files delete my videos?

No. Render files are temporary previews, not your footage or edits. Deleting them frees significant space, and iMovie rebuilds them automatically the next time you open the project.

Where is the iMovie library stored on a Mac?

The iMovie library is stored at ~/Movies/iMovie Library.imovielibrary — open Finder, click Movies in the sidebar, and look for the purple star icon.

Can I move my iMovie library to an external drive?

Yes. Drag the iMovie Library.imovielibrary file onto an external drive, then double-click it there to reopen it. iMovie will read and write from the external drive, freeing your internal storage.

Once iMovie is tidy, the next-biggest space hogs are usually other media caches. Clear them with how to clear the Final Cut Pro media cache and how to clear Adobe Premiere / After Effects media cache, and if your storage bar still shows a mysterious bulge, read mysterious System Data on Mac: how to safely clean the disk. For a structured walkthrough, follow the clean up phone storage hub, and if you also shoot and edit on your phone, Cleanor finds the large videos and duplicate clips crowding your camera roll — scanned locally, nothing uploaded.