I’ve recently gotten a number of emails from people with iTunes issues where album artwork doesn’t display correctly. There’s a simply trick that can resolve these issues: it involves deleting a cache folder that iTunes stores on your computer to speed up the display of album art.
When you view files in iTunes, the app checks to see if there is album artwork embedded in the files, or downloaded separately (for purchased files). If so, it creates a cache file of the artwork, so it doesn’t have to read the music files every time it displays them. I’ve found that, when I have issues with album art not displaying correctly, or not displaying at all, deleting this folder – stored in your iTunes folder – resolves them.
The folder is in ~/Music/iTunes/Album Artwork; that’s the iTunes folder in the Music folder in your home folder (the one with your user name and the house icon):
Delete the Cache folder, empty the Trash, quit iTunes and relaunch it. You’ll notice that iTunes lags a bit when displaying a lot of content; as I said above, it has to extract the artwork from the files, and this takes a bit of time. But over time, the cache will be rebuilt, and this can fix some issues with album artwork displaying incorrectly.
Don’t delete the other folders; they contain artwork for purchased tracks, where the artwork isn’t embedded in the files, or other items in the cloud.
If you often add music or other content to your iTunes library and remove it, I’d recommend deleting this folder from time to time, if only to save space. It will contain cache files for items you’ve deleted, and, as you can see above, it can take up a lot of space. Mine is more than 4.5 GB, for a library of some 70,000 items.
Note: as one commenter pointed out, deleting this folder resolved an issue where iTunes was slow to launch. I hadn’t thought that it might have other effects on iTunes, so if you have any problems with iTunes running slowly, you might want to try deleting the folder. It can’t hurt; as I say above, iTunes just recreates the cache files.