Is it safe to delete video editing cache files? (Premiere, After Effects, DaVinci Resolve)

Yes. Media caches, disk caches and render caches are working copies that video apps build from your original footage. Deleting them doesn't touch your projects or your media. The cost is time: the app has to re-index, re-conform or re-render what it needs next time you open a project. Never delete cache files by hand while the app is open.

Quick verdict:

Safe: Adobe Media Cache Files, Media Cache and Peak Files (Premiere, After Effects, Media Encoder), with the apps closed.
Safe: the After Effects disk cache, best emptied from inside After Effects.
Safe: DaVinci Resolve's CacheClip folder, best cleared with Playback → Delete Render Cache.
Not a cache, don't delete: your project files, Auto-Save folders, original footage, and Resolve's project database.
Think first: Resolve optimized media and proxies. They are rebuildable too, but it can take hours.

What are video editing caches?

Editing apps don't play compressed camera files directly at full speed. They create helper files: indexes, decoded audio, waveforms and pre-rendered frames. These pile up for every clip you've ever imported, including projects you finished years ago.

Adobe Media Cache (Premiere, After Effects, Media Encoder)

Adobe apps share one media cache. When you import video or audio, they write conformed audio (.cfa), peak files for waveforms (.pek), indexes and a database that tracks them. Adobe lists the default locations:

System	Folder
Mac	`~/Library/Application Support/Adobe/Common`
Windows	`C:\Users\<your name>\AppData\Roaming\Adobe\Common`

Inside you'll find Media Cache Files, Media Cache and Peak Files. You may have moved the cache elsewhere in the preferences: in Premiere, check Edit → Preferences → Media Cache (Windows) or Premiere → Settings → Media Cache (Mac).

After Effects disk cache

After Effects also keeps a disk cache of rendered frames so previews are faster. It's persistent: frames stay between sessions and can be reused across projects. According to Adobe, its default maximum size is 10% of the drive, up to 100 GB. The folder is shown in Edit → Preferences → Media & Disk Cache (Windows) or After Effects → Settings → Media & Disk Cache (Mac).

DaVinci Resolve CacheClip

Resolve stores its render cache (Smart or User cache) in a folder called CacheClip. It lives in the cache files location set in Project Settings → Master Settings → Working Folders, which by default is the first volume listed in DaVinci Resolve → Preferences → System → Media Storage. That's why the cache can end up on your system drive without you noticing. Optimized media and proxies are kept in their own folders nearby.

How much space does it use?

These folders can grow to tens or hundreds of gigabytes if you edit a lot of footage.

Mac: in Finder, choose Go → Go to Folder, paste the path, then select the folder and choose File → Get Info. Or in Terminal: du -sh ~/Library/Application\ Support/Adobe/Common/*
Windows: paste %AppData%\Adobe\Common into File Explorer's address bar, then right-click each folder and choose Properties.
Resolve: open the Working Folders setting to see where CacheClip is, then check that folder the same way.

A disk space analyzer is useful because caches end up in different places, often on different drives. With SquirrelDisk, scan the drive or click A folder and paste %AppData%\Adobe on Windows. On a Mac, scan your home folder and look under Library/Application Support/Adobe. The chart shows at a glance whether the media cache, a CacheClip folder or old render files are what's filling the disk.

How to delete it safely

Premiere

Open Premiere and choose File → Close All Projects.
Go to Edit → Preferences → Media Cache (Windows) or Premiere → Settings → Media Cache (Mac).
Next to Remove Media Cache Files, click Delete.
Choose Delete unused media cache files (only for media that can't be found any more) or Delete all media cache files from the system, then OK.

These are Adobe's steps. Adobe suggests restarting Premiere and doing this before opening any project when you want to remove everything.

After Effects

Disk cache: choose Edit → Purge → All Memory & Disk Cache, or click Empty Disk Cache in the Media & Disk Cache preferences. Purging in one version of After Effects doesn't empty the cache of other installed versions.
Media cache: in the same preferences, Clean Database & Cache only removes files for footage whose source can't be found. Connect all drives with footage you still use first, or their cache will be removed too.

DaVinci Resolve

Open the project.
Choose Playback → Delete Render Cache, then All (everything for this project) or Unused (only what the current timelines no longer need).

Repeat for other projects, or delete old cache folders by hand as below.

By hand

Quit Premiere, After Effects, Media Encoder and Resolve. Deleting cache files while an app is open can confuse its database or cause errors.
Open the cache folder and delete the contents: Media Cache Files, Media Cache and Peak Files for Adobe, or the subfolders inside CacheClip for Resolve.
Empty the Trash or Recycle Bin.
Open your project and give it time to rebuild before judging playback.

With SquirrelDisk you can drag these folders into the collector and choose Delete for good, or Move to Trash. It asks for an extra confirmation because they're inside ~/Library or AppData, which is expected.

What you should not delete

Project files and Auto-Save folders. Premiere's .prproj, After Effects' .aep and their auto-saves are your work, not cache.
Original footage. Obvious, but caches often sit right next to media on the same drive.
Resolve's project database or library. Projects live there. Only clear CacheClip, never the database folder.
Optimized media and proxies, mid-project. They can be regenerated, but on a long project that can take hours. Delete them after delivery.

If something looks wrong after clearing a cache, like missing waveforms or red render bars, it's normally just the rebuild. Let the app finish indexing.

How to stop it growing back

Premiere: under Media Cache Management, choose Automatically delete cache files older than (default 90 days) or Automatically delete oldest cache files when cache exceeds (default 10% of the drive). Adobe notes that "Do not delete cache files automatically" is the default.
After Effects: lower Maximum Disk Cache Size, or point the disk cache at a fast second drive.
Resolve: set the first Media Storage volume, or the Working Folders cache location, to a fast drive other than your system drive.
After delivering a project, clear its cache and render files, and archive or delete its optimized media.

Other apps keep caches too. See Mac cache files and Windows Temp files for the rest.