It appears that Steam disables the ENTIRE ~/Library/Application Support folder from Time Machine backups.

RUDE! And disconcerting. That folder contains things like messages, emails.... all sorts of stuff you might need to restore from backup.

It does this without you knowing. Worse, you figure it out and re-enable, it changes it back to excluded. Oh, and you can't see this in the system settings UI for Time Machine either.

I only found it when I went to exclude Steam's directory in Application Support. Application Support was grayed out completely in the exclude files and folders.


To check if this is the case for you, run this command in terminal:

tmutil isexcluded ~/Library/Application\ Support

It will come back with a message like `[Excluded]`


To fix this infuriating and hostile behavior, runt this command in terminal:

sudo tmutil removeexclusion ~/Library/Application\ Support


Note that this will only add Application Support back to Time Machine backups until you run steam again.