On April 10, 2018, Valve announced a change to Steam’s default privacy settings. Settings have better descriptions, you can keep your total game playtime hours private, it is possible to choose who sees your game details like achievements and playtime, and you can tell if you can be seen “in-game” in a title or not.
An upcoming Steam update will offer people a new status option. Right now, someone can set themselves as online, away or offline when logged into Steam, with offline letting you appear offline, but not letting you see your friends list. In the future, invisible will let you appear offline, but still access friends list features.
As an aside, Steam Spy has responded to the privacy update with some rather unfortunate news. On Twitter, Sergey Galyonkin stated the site would be shutting down due to Valve making everyone’s Steam game library hidden by default as part of the new privacy settings. Steam Spy used that information to show game data regarding owners, playtime and score rank.