I'm 'away' for a week and would like some friends not to know I'm playing games. What does blocking a friend actually do?
I'm just looking for it to show me as offline and not show what game I'm playing or if I'm online or not.
Steam – Impact of Blocking Someone
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Related Solutions
VALVe recently added the function so that it is possible to earn achievements in offline mode. They did not announce it, though, for some reason. One can only speculate about this.
The condition for this to work is that, while online, you have run the game once or viewed the details in your library. Otherwise Steam wouldn't "know" that there are achievements in the first place.
Source: http://forums.steampowered.com/forums/showthread.php?p=29035241
Also, note that achievements you earn do not register onto your Steam account until you connect back to the Steam service (have an internet connection) and are dated at the time of reconnection.
Since a recent update, you can now set it so that only your friends, or no-one can see what you're playing.
Go to the Steam community settings page here, it can be found at that link or as this answer states, on Steam go to Profile > Edit Profile > My Privacy Settings > Game details
At Game Details you can choose between public, friends only or private.
This category includes the list of all games on your Steam account, games you’ve wishlisted, your achievements and your playtime. This setting also controls whether you’re seen as "in-game" and the title of the game you are playing.
Best Answer
To specifically answer your question at hand, blocking someone will make it so you appear offline to them. No notifications are sent regarding your status or game-playing. They WILL still be on your friends list (and you'll be on their list), so you have easy access to unblock them at any time. Blocked players who are unfriended are still blocked, and they cannot send you another friend request.
I have personally used 'blocking' to temporarily set myself as offline to a specific individual or small group of people while being online to everyone else. I have also personally verified this through my wife's steam account too.
Just keep in mind your steamcommunity profile is public, so if anyone happens to visit your browser profile (e.g. steamcommunity.com/id/yourprofileid) while playing a game , it will say you're in-game. I don't think that will really be a problem, as I'm assuming there's not really a reason for the people you're blocking to visit your browser profile. Setting your status to 'Appear Offline' DOES make you offline across the board, including steamcommunity.com.
Additional note: The other answers here spurred me to do some additional testing with this. If the person you're blocking is online when you block them. You will permanently be 'Online' to them until they close or restart Steam. If you want to covertly block someone, do so while they're offline so when they log in next you will appear offline to them.
If you're not patient enough to wait for someone to go offline, you can do the following:
This effectively allows you to block players while you appear to be offline.