Purpose of '~/.cache' directory and when is it safe to delete?

Question

What is the purpose of every user's ~/.cache directory?

Under which circumstances can it be deleted, when should one be careful about its contents?

Answer 1

This is by no means a definite answer.

According to the XDG Base Directory Specification, $XDG_CACHE_HOME which defaults to $HOME/.cache holds

[...]user-specific non-essential (cached) data[...]

It is however not specified what constitutes 'non-essential data'. Furthermore an application might not play by freedesktop rules and put whatever it wants in .cache.

Browsing through my cache folder, I find things like

• Browser caches. Safe enough to delete.
• Thumbnails. Will be recreated if deleted.
• software-center. Wasn't sure about that. Contains a file apthistory.p with your - well - history of apt. Moved it out of the way and it was recreated on the next start of the Ubuntu Software Center.
• I guess the Software Updater stores package lists apt-file. Will be downloaded anew if deleted.
• icon-cache. Like thumbs, will also be recreated.
• compizconfig-1. Contains binary files; compiz seems to cache its configuration in optimized form from ~/.config/compizconfig-1.
• dconf. This directory actually doesn't belong to $USER but root. Mine contains a single non plaintext file user. Since you can't delete it anyway without sudoing... No problem.
• And some more directories which I don't deem critical.

In summary, I believe it perfectly safe to empty the cache folder. In fact I do this from time to time and never experienced faulty behaviour afterwards.

This is not a guarantee though, just my two cents and a (somewhat) educated guess.