A video editor's project folder is mostly files it can regenerate
Render caches, generated files and optimised media are usually larger than your footage. Which of them come back on their own, and which do not.
Video is the fastest way to fill a Mac, but the footage is often not the problem. Editors generate optimised copies, proxies, render files and thumbnails, and by default they keep all of it next to your project indefinitely.
What is regenerable and what is not
| Kind of file | Comes back | Cost of regenerating |
|---|---|---|
| Render and cache files | Yes | Rendering time on next playback |
| Optimised or transcoded media | Yes | A slow conversion pass |
| Proxy media | Yes | Another conversion pass |
| Thumbnails and waveforms | Yes | Seconds |
| Original footage | No | Gone for good |
| The project or timeline file | No | Your edit, gone |
Everything in the top half is disposable. The bottom two rows are the only things in a video folder that cannot be recreated, and they are usually the smallest files in it.
Where each editor puts them
Final Cut keeps render files inside the library bundle, and has a Delete Generated Library Files command in the File menu that removes them properly. iMovie keeps its own library in ~/Movies with the same idea. Most others use a cache folder inside or beside the project.
du -sh ~/Movies/* 2>/dev/null | sort -h | tail -10For a Final Cut library, right click it in Finder and choose Show Package Contents to see the render folders inside. Removing them from Finder works, but the menu command is better because it also updates the library's own bookkeeping.
The habit that prevents it
- Keep source footage on an external drive and reference it rather than copying it into the library.
- Delete generated files when a project is finished, not while you are still editing it.
- Export the finished video, archive the project, then remove the caches.
- Check
~/Moviestwice a year, since old projects are kept out of caution and never revisited.
If the footage itself is the problem rather than the caches, moving it off the internal drive is the answer, and what moves safely to an external drive covers which folders tolerate that and which do not.
Common questions
Can I delete Final Cut render files?
Yes. Use File, Delete Generated Library Files inside Final Cut, which removes render and optimised media properly and updates the library. The files are recreated when you next play back or export, at the cost of rendering time.
Why is my Movies folder so large?
Usually because editors store generated files next to your projects: render caches, optimised copies, proxies and thumbnails. On a Mac measured in September 2026, one editor's folder was 3.2 GB with only a small fraction of that being source clips.
Is it safe to delete an iMovie library?
Only if the projects inside it have been exported. The library holds your timelines as well as media, so removing it removes the edits themselves, which nothing can regenerate.
Should I keep video footage on an external drive?
For anything you are not actively editing, yes. Editors can reference media rather than copying it in, which keeps the internal drive free. Original footage is the one thing in a video workflow that cannot be regenerated, so it needs a backup either way.