Photo editors keep a cache per image, and it outlives the edit
Affinity, Pixelmator and similar tools cache previews, history and scratch data. What each keeps and which folders are safe.
Image editors cache aggressively because opening a large layered document should be instant. What they cache is per document and per session, and much of it survives after you close the file.
Where the caches are
du -sh ~/Library/Containers/*[Aa]ffinity* \
~/Library/Containers/com.pixelmatorteam.* \
~/Library/Caches/*hoto* 2>/dev/null | sort -h| What | What it is | Safe to clear |
|---|---|---|
| Preview and thumbnail cache | Rendered previews of documents | Yes |
| History and undo data | Per document editing history | Yes, when the document is closed |
| Scratch data | Working space for large documents | Yes, when the app is closed |
| Autosave and recovery | Unsaved states | No while any document is unsaved |
| Presets and brushes | Things you installed or made | No |
Scratch space and the disappearing gigabytes
Editing a large layered document can consume many gigabytes while the app is open and release them when it quits, exactly like Photoshop's scratch disk. If space vanishes while you work and returns afterwards, that is the mechanism rather than a problem.
The recovery folder deserves care
Recovery data is the one thing in this category worth protecting. It is what restores your work after a crash, and clearing it while a document is open and unsaved is the one action here that can genuinely lose work. Quit the app cleanly first, which is also when most of these folders empty themselves.
Documents are usually the larger number
A layered document with several high resolution photos in it is hundreds of megabytes, and a folder of them dwarfs any cache. Flattening exports for delivery and archiving the layered originals to an external drive is the same pattern as every other creative workflow on this site.
Common questions
Where do photo editors keep their caches on a Mac?
Inside their containers under ~/Library/Containers, with some also using ~/Library/Caches. Sandboxed apps from the App Store keep everything inside the container.
Is it safe to delete a photo editor's cache?
Preview caches, history and scratch data are safe once the app is closed. Recovery data should be left alone while any document is unsaved, since it is what restores work after a crash.
Why does my disk fill while editing images?
Because editors use scratch space for large layered documents, which can be many gigabytes while the app is open and is released when it quits. It is the mechanism working rather than a fault.
What uses more space, the editor or my documents?
Usually the documents. A layered file with several high resolution images is hundreds of megabytes, and a folder of them exceeds any cache the app keeps.