After many months of beta testing, Valve has made its Steam Family Sharing program available to all Steam users.
For those unaware, Steam Family Sharing allows you to share your entire library of games with up to five users spread across ten authorized machines. In almost all cases, playing a shared title offers the exact same experience as playing a game that you’ve purchased yourself. All game progress is still saved via Steam Cloud services and Steam Achievements are earned only by the user actually playing.
Games associated with another user’s library may only be played, however, while that library is not in use. If any game from the host library is accessed while another user is playing, that user will be given a few minutes warning that his or her game session will be shut down unless they purchase the game.
While all of this sounds great in theory, actually sharing your game library with another user is quite a complicated process, and one that may require sharing your account password. If that possibility doesn’t scare you, you can follow the detailed guide below to find out how to successfully access another user’s library.
Steam Family Sharing How-to Guide
If you want to be able to play games that belong to a friend or family member (or vice versa), you must sign into Steam on the specific computer that you want to use with your friend’s Steam log-in information at least one time.
Unless you actually live with this person, this process will involve asking for your friend’s Steam username and password. It will also involve asking said friend for the five digit verification code that is required by Steam when attempting to sign into the program for the first time on an “unauthorized” computer. Remember when I told you this was complicated?
Once you have successfully logged into the other user’s Steam account on the specific machine that you wish to use, you must do one more thing in order to access their library. While logged in with their information, you must select “AUTHORIZE THIS COMPUTER” (see below).
Once this has been done, and after you have logged back onto the same computer with your account information, you should now see your buddy's Steam user name under “AUTHORIZED ACCOUNTS.” Because you are nice, you should select this box and return the favor of Steam Family Sharing.
All you have to do now is ask your friend to check the box next to your name. Remember, however, that they will only see your username if they have gone through all of the steps described above on one of their computers.
Once everything is said and done, you should now see under the “Library” drop down menu (see below) an option to view only a specific user’s game library. Judging by the content of my brother’s library, it appears to only show games that I have not yet purchased.
Well, there you have it. It’s certainly not pretty, but it’s also understandable why Valve doesn’t want to make it super easy to share your games with multiple people. In addition to potential financial concerns, Valve has made it clear that any Valve Anti-Cheat (VAC) infractions resulting from a friend's actions will result in punishment being doled out to the original account holder. While it would be nice if you could simply right click on a person in your Steam friends’ list and select “share library,” the extra step of having to provide your account information makes you think twice about giving this privilege to someone.
Source: Steam Family Sharing