Steam Family Sharing has finally come out of beta and is available to everyone on Steam. The Service allows you to so share your entire library with up to 5 different accounts across 10 devices. This feature requires that Steam has an active internet connection in order to access the family library. There will be some titles that are not available to family sharing however, any game that requires an extra client, Origin for example, will not work across Family Sharing. Downloadable content will also be shared so long as the main game is not owned buy the guest.
To enable Family Library Sharing, first be sure you have Steam Guard security enabled via Steam > Settings > Account in the Steam Client. Then enable the sharing feature via Settings > Family, (or in Big Picture mode, Settings > Family Library Sharing,) where you’ll also authorize specific computers and users to share.
The main account holder who is sharing the games library will always have priority access, should the user wish to play a game that is in use by a guest the guest will have a few minutes to either purchase the game for themselves or quit the game. A shared library may only be accessed by one user at a time.
Now for a quick warning. Your Family Library Sharing privileges may be revoked and your account may also be VAC banned if your library is used by others to conduct cheating or fraud. Additionally, VAC-banned games cannot be shared. Steam recommends you only authorize familiar computers you know to be secure.