The short version
- Every editing app splits into two kinds of files: generated (render, cache, proxy, optimized) and original (your footage and project database).
- Generated files always rebuild from originals. That makes them safe to delete, at the cost of some rebuild time.
- Each app has a built-in command to clear its generated files. Use it, rather than hunting in Finder.
- The one rule that covers all four apps: never delete source media or the project library.
The one idea that makes this safe
There is a single distinction underneath every video app, and once you hold it, cleaning up becomes almost risk-free. On one side are generated files: render files, cache files, optimized media, proxies, preview frames. The app made these from your footage to make editing smooth, and the app can make them again. On the other side are originals: the camera footage you imported, and the project database that holds your edits, your timeline, your grades. These cannot be regenerated. If they are gone, they are gone.
Apple states this plainly in its Final Cut documentation: when you delete generated files, "original media files are not deleted, so you can always regenerate render files from the original media." That sentence is the whole philosophy. Clean the generated side freely; never touch the original side.
Final Cut Pro
Final Cut stores a project as a library, a .fcpbundle package that lives by default in your ~/Movies folder. Inside it are render files, and often optimized and proxy media too. To see how much space the generated files take, select a library in the sidebar and look at the Cache section of Library Properties.
To clear them, select the library and choose File › Delete Generated Library Files. The dialog lets you delete render files, optimized media and proxy media independently. For render files you get a further choice: delete only the unused ones, or all of them.
Render files regenerate automatically the next time you open and work on the project. Optimized and proxy media also come back from your originals, but you have to regenerate them manually, so only clear those if you are willing to rebuild them before your next proxy edit.
Do not delete original media stored inside the .fcpbundle (managed media). The Delete Generated commands never touch it, but a manual trip into the package can. If it is your only copy of the footage, losing it is permanent.
Adobe Premiere Pro and After Effects
Premiere and After Effects share a media cache. When you import a clip, Premiere builds accelerator files so playback and scrubbing are smooth: conformed audio (.cfa), peak waveform files (.pek), and index files. By default they live in ~/Library/Application Support/Adobe/Common, split into two parts: Media Cache Files (the accelerator files) and Media Cache (a database of links to them). That database is shared across Premiere, After Effects and Media Encoder.
Clear it from inside the app: Premiere Pro › Settings › Media Cache, then Delete. Choose "Delete unused media cache files" to remove only entries whose source media is gone, or delete all of them. Close all projects first if you want a clean sweep. After Effects has its own Disk Cache of rendered preview frames, cleared from After Effects › Settings › Media & Disk Cache › Empty Disk Cache.
First, before cleaning the database, connect the drives holding your current source media. If Premiere thinks footage is missing, it purges that footage's cache and you pay to re-conform it later. Second, do not empty the whole Adobe/Common folder in Finder. It also holds LUTs, Motion Graphics templates and plug-in data. Delete only the cache subfolders.
Premiere can also clean up on its own. In the Media Cache settings you can have it automatically delete cache files older than a set age (90 days by default) or trim the oldest files once the cache grows past a share of the disk (10 percent by default).
DaVinci Resolve
Resolve generates render cache (stored in a CacheClip folder as .dvcc files), plus optimized media and proxy media in their own folders. All three follow the Cache Files Location set in Project Settings › Master Settings › Working Folders, which on a Mac usually sits under ~/Movies. The surest way to know where yours is: read it off that settings page.
Clear render cache from Playback › Delete Render Cache (Unused, All, or Selected Clips), and optimized media from Playback › Delete Optimized Media. Resolve 18.5 and later add a cross-project Manage Cache Data window so you can see sizes and clear across every project library at once.
If you delete a Resolve cache folder in Finder rather than from the menus, quit Resolve first. The cache location is tracked in the project database, and you cannot simply drag the folder elsewhere; repoint it in Working Folders instead.
Gallery stills (your saved grades and reference frames) and the project library/database are user data, not cache. They hold work you cannot recreate. A cleaner should surface them as "your data," never queue them for deletion.
Lightroom Classic, and the one that bites people
Lightroom keeps previews next to your catalog in a Previews.lrdata package. These standard and 1:1 previews can grow to tens of gigabytes, and they are completely safe to discard; Lightroom rebuilds them on demand, with a short slowdown while it does. There is also a separate Camera Raw cache (5 GB by default) you can purge from Preferences.
But there is a sibling file, Smart Previews.lrdata, that looks just as disposable and is not. Smart Previews are lightweight DNG copies that let you edit photos when the originals are offline, say on a disconnected external drive. If your originals are not connected, the Smart Preview is the only editable copy you have. Delete it then, and you lose the ability to edit those photos until the originals come back.
Looks disposable
Smart Previews.lrdata sits right next to the regular previews and has the same extension, so it is easy to assume it is just more cache.
Sometimes essential
When originals are offline it is your working copy. Safe to delete only if your originals are always connected. Your edits are never lost either way; they live in the catalog.
The .lrcat catalog file holds every edit and every piece of metadata for your whole library. It is the single most important file Lightroom has. Clearing previews is fine; the catalog is untouchable.
Photoshop scratch files
Photoshop uses a scratch disk as overflow memory, and it writes temporary files there. If Photoshop crashes or does not quit cleanly, it does not always delete them, so they pile up and eventually trigger "scratch disk full" errors. The safe cleanup is to quit Photoshop completely, then remove the leftover Photoshop Temp files from the macOS temp directory. While Photoshop is running you can also use Edit › Purge › All, but save first, because purge is irreversible.
Never delete active Photoshop Temp files while Photoshop is open. They are in use, and removing them can corrupt your session. The exact temp path varies per session, so let the app be closed and search for the named files rather than hard-coding a folder.
A quick reference
| App | Safe to clear (rebuilds) | Never delete |
|---|---|---|
| Final Cut Pro | Render files (auto), optimized & proxy media (manual rebuild) | Original media in the library |
| Premiere / After Effects | Media Cache Files, AE Disk Cache | LUTs, templates, plug-in data in Adobe/Common |
| DaVinci Resolve | Render cache, optimized & proxy media | Gallery stills, project library |
| Lightroom Classic | Previews.lrdata, Camera Raw cache | .lrcat catalog; Smart Previews if originals are offline |
| Photoshop | Photoshop Temp files (app closed) | Active temp files while running; unsaved documents |
Let the labels do the thinking
StorageSage recognises the generated files of all these apps and labels them Safe or Rebuilds, while flagging originals, gallery stills and catalogs as Review so they are never preselected. Everything it removes goes to the Trash first.
Download for macOSSources
- Apple — Final Cut Pro User Guide: managing render files; creating optimized and proxy files.
- Adobe — Premiere Pro and After Effects media cache documentation (clearing, automatic management, Media & Disk Cache); Lightroom Classic performance and Smart Previews; Photoshop scratch disk troubleshooting.
- Blackmagic Design — DaVinci Resolve Reference Manual, Working Folders; Cache management.