iTunes has long had an Album Artwork folder (in your home folder, in /Music/iTunes), which held a few sub-folders for cached artwork, downloaded artwork, etc. But recently, that folder has added a number of sub-folders. They all contain album artwork, but each subfolder has artwork from a different source, or used for a different purpose.
I’ve looked through the contents of these folders on my two Macs in order to determine what the artwork in each folder is used for. Several of the folders are empty, so I’m not sure what they should hold. Here is a list of what I’ve figured out so far. If you see artwork in any of the folders which are empty for me, have a look and see what they contain. (iTunes artwork cache files have an .itc extension. The only app I have that can display these files is Graphic Convertor.)
- Cache: This folder contains cached copies of artwork taken from your media files. This cache allows iTunes to display artwork more quickly than if it had to extract it from your files each time it is displayed.
- Cloud: This folder holds a cache of artwork for tracks in your iCloud Music Library, but for which you don’t have local copies. iTunes downloads artwork from the cloud so it can display this artwork for these tracks. If you don’t have iCloud Music Library turned on, this folder is empty.
- Cloud Purchases: This is artwork for items you have purchased that are still in the cloud, and that you have not downloaded.
- Custom: Artwork that you’ve added to a playlist, by dragging it to the album artwork in the info bar above the playlist when in Playlist view.
- Downloaded: This folder contains a number of different items. Some of the artwork is for podcasts or iTunes U courses that I have downloaded, some are four-album graphics as used for playlists. I also see thumbnails for some albums that I have purchased from the iTunes Store, and perhaps for albums where iTunes has downloaded artwork. There is also artwork for audiobooks that I have purchased from Audible.
- Editorial: This folder holds artist photos that display for some artists when you view their music in Artists view. It’s not clear which artists have these photos; many artists who I’d expect to have custom photos on the iTunes Store don’t display such photos when I view their music. For some reason, this folder empties very quickly, even if you’re viewing an artist with such a photo.
- Generated: This seems to be artwork that is applied to the info header for playlists in Playlists view. The graphics in this folder are either four-album montages or single album covers, the latter corresponding to playlists I have which contain only one album.
- Local: This folder is currently empty; I have no idea what should be here. Only my MacBook, which has iCloud Music Library turned on, displays this folder; my iMac does not.
- Remote: This folder contains artwork from libraries you load with iTunes Home Sharing.
- Store: This folder is currently empty; I have no idea what should be here.
Interestingly, only some of these folders are backup up by Time Machine; it looks as though Time Machine knows to not back them up, because they are essentially temporary folders, or folders whose content can be easily recreated. The folders I see in my Time Machine backups are Cloud, Cloud Purchases, Custom, Downloaded, and Remote. It’s actually a good thing that Time Machine does not back up the Cache folder, which is the largest; that would eat up a lot of backup space. On my iMac, that folder is 4.46 GB, and on my MacBook, with a much smaller library, it’s just over 2 GB.
If you have any files in the folders which are empty for me, and can figure out what the artwork is for and where it comes from, post a comment so I can update this article.