XDG just extends the traditional Unix approach to home directories. $XDG_CONFIG_HOME is equivalent to /etc. It has small files you probably want to back up. $

XDG just extends the traditional Unix approach to home directories. $XDG_CONFIG_HOME is equivalent to /etc. It has small files you probably want to back up. $XDG_DATA_HOME is equivalent to /var. It has potentially large files you might want to back up. $XDG_CACHE_HOME is equivalent to /var/cache. It has potentially large files you probably don't want to back up. You can delete them if you need space.