Sharing is caring, and there's no better way to show your friends and family you care than to let them have a taste of your abundant Steam library. Today, after six month in beta, Valve announced Steam Family Sharing is available to all Steam users.
Family Library Sharing allows you to share your Steam library with up to 10 computers at a given time, and for up to five accounts that may then use your game library on any of those computers.
Only one account can play games from the library at a time, and the primary account holder always has access over other users. If you start playing a game while one of the people you shared the library with is already playing, he or she will have a few minutes to either save and quit or purchase the game and continue playing. Also note that games that require an additional third-party key, account, or subscription in order to play can't be shared.
Valve also warns to be cautious about who you share your library with, and not to let someone you don't know into your account to authorize their computer. “Your account may also be VAC banned if your library is used by others to conduct cheating or fraud,” Valve says. “Additionally, VAC-banned games cannot be shared. We recommend you only authorize familiar computers you know to be secure. And as always, never give your password to anyone.”