Premiere caches at four different layers and most "clear cache" tutorials only mention two of them. The result is editors clearing the obvious cache, getting confused when their projects still feel sluggish, and eventually nuking something they shouldn't have.
Here's what each cache layer does, what's safe to delete, and the order to clear them in if you want your projects to come back online cleanly.
The Four Cache Layers
Think of Premiere's caches like the layers a sound mixer keeps for a feature: production audio stems, ADR pre-dubs, music stems, the final mix. Each layer is built from the layer below it, and you can rebuild the higher ones if you have the lower ones intact. Caches work the same way.
Media Cache (.cfa and .pek files) is the audio waveform and conformed audio data Premiere generates the first time it sees a clip. The .pek file is the visual waveform you see in the timeline. The .cfa is conformed audio in a format Premiere can scrub instantly. These get rebuilt automatically if deleted.
Render Cache (preview files) is the rendered video for sections you've manually rendered with Sequence > Render In to Out. They live next to your project file by default, in a folder ending in .Pre or in the Adobe Premiere Pro Preview Files folder. Deleting them doesn't break anything, but you'll have to re-render the timeline.
Auto-Save backups are full copies of your .prproj saved every fifteen minutes by default. They live in the Adobe Premiere Pro Auto-Save folder next to your project. These are not technically "cache," but they pile up like cache and most cleanup guides ignore them.
The Mercury GPU cache is invisible. It's a per-machine cache of GPU shader compilations and effect lookups, stored deep in the Adobe app support folder. It can grow to 5 to 20 GB without you noticing. Adobe rarely mentions it.
What's Safe to Delete vs What Kills Your Project
Quick rundown:
- Media Cache: safe. First reopen will be slow because Premiere reconforms audio, but no project data is lost.
- Render Cache: safe. You re-render. No data lost.
- Auto-Save: keep at least two weeks. This is your only fallback if a project corrupts. Don't aggressively prune.
- GPU Cache: safe. Premiere rebuilds it on first launch.
What you should never delete: the .prproj file itself, the project's own auto-save folder if you're actively editing, anything in your project's Captured Audio or Captured Video scratch folders, or the Adobe Premiere Pro Preview Files folder for a project you're still cutting.
The Safe-Clear Procedure
Do these in order:
1. Quit Premiere completely. Not just close the project. Quit the application. If Premiere is running, it has open file handles on cache files and you'll get partial deletes that confuse the engine on next launch.
2. Clear the Media Cache. Go to ~/Library/Application Support/Adobe/Common/Media Cache and ~/Library/Application Support/Adobe/Common/Media Cache Files. Delete the contents of both folders, not the folders themselves. On Windows, the path is C:\Users\<You>\AppData\Roaming\Adobe\Common.
3. Clear the Render Cache for the project. Open Finder and navigate to your project folder. Find the folder named [Project Name] Auto-Save and the folder ending in .Pre or "Adobe Premiere Pro Preview Files." Delete the .Pre folder if you're done with the renders, or leave it if you want playback to stay smooth on next open.
4. Clear the GPU cache (optional, do this if you're seeing render errors). It lives at ~/Library/Caches/Adobe/Common/Mercury Transmit on Mac. Delete the contents.
5. Restart Premiere and reopen the project. Expect the first launch to be slow. Premiere will reconform every audio file in the project, which on a big project can take ten to twenty minutes. Walk away. Get coffee.
When it finishes, you'll be at a clean state. Playback will be cold for a session as renders rebuild, but the project is intact.
Where Premiere Defaults Put Cache (and Why You Should Change It)
The default Media Cache location is your boot drive's home directory. On a 512 GB MacBook Pro running a long-form project, that cache can fill your boot drive in a week. When the boot drive is full, macOS starts swapping, and Premiere starts crashing.
Move it. Open Premiere > Preferences > Media Cache. Change Media Cache Files and Media Cache Database to a path on a fast external SSD. Something like /Volumes/CacheSSD/Premiere Cache works. The drive should be SSD because cache reads happen constantly during playback. Spinning disks will tank your performance.
Set retention rules in the same panel. "Automatically delete cache files older than 90 days" is a sane default. If you're juggling many short projects, drop it to 30 days. If you keep returning to long-form projects, leave it at 90.
If you want a deeper look at why the boot drive matters so much for editing performance, our breakdown of slow Premiere playback covers the disk side of the equation in detail.
Why "Just Clear Cache" Often Doesn't Help
Editors clear cache because they think the cache is causing slowdowns. Usually it's not. The cache is a symptom, not the cause. You're slow because:
- Your project has too many bin items (every one gets indexed on open).
- Your media drive is also your cache drive, and they're competing for I/O.
- Your boot drive is full, and the OS is swapping.
- Your project file itself is bloated with thousands of unused clips.
That last one is the silent killer. Clearing cache buys you a few hours of speed before the cache rebuilds and you're slow again. Removing unused media from the project is permanent.
Clip Sweeper reads your .prproj files and tells you exactly which clips are used in any sequence and which aren't. Before your next cache clear, it's worth checking how much of what's loading on every project open is footage you don't actually need on the timeline. Smaller projects open faster, save faster, and crash less.