What's the quick answer?
Backblaze backs up /Users/yourusername/Library or ~/Library
Backblaze does not back up /Library
What's the difference between those two Library folders?
Mac OS X contains two Library folders:
• A user level Library for each user at /Users/yourusername/Library or ~/Library
• A top level Library folder at /Library
The user level Library contains items like settings for Mail, Safari, and many third party apps; calendars, address book, emails, etc. A significant amount of unique, user data is stored in that folder.
The top level Library folder contains primarily non-unique operating system files and caches.
What Library does Backblaze back up?
By default, Backblaze backs up all user level Library folders at /Users/yourusername/Library or ~/Library
This means that user-created data, like settings/preferences, mail, browser bookmarks, calendars, address book data, widgets, etc. are all backed up by Backblaze.
What Library doesn't Backblaze back up?
Backblaze won't back up the top level /Library folder, as it primarily contains non-unique data. By not backing up this data, it makes your backup complete faster, with less bandwidth used. In turn backups use less space on our servers storing non-unique data, so we can continue to offer a low priced, unlimited storage product.
The data in /Library is re-created when an operating system is installed, and when applications are reinstalled. Users do not have to directly interact with files in /Library in most circumstances.
If you have data in the top level Library folder that you wish to back up, make a copy of it to a location that Backblaze does back up. There is no way to override /Library to include it in your backup.