Global option You can now allow downloads during any gameplay from the downloads settings: Per game option You can now tell Steam to continue downloading updates/games while playing games from your games' properties.
Note that this setting is not available for non-steam games , which will always use the global setting.
gaming.stackexchange.com/users/51318/3ventic
The way I do it is: Pause all of the downloads manually.
Launch
the game I want to play.
Alt-Tab back to Steam window, resume all downloads manually.
Alt-Tab back to the game and enjoy.
It seems that it only stops the download for you on launching a game.
I have not found an "official" way to do it, but this way works until they give us one.
gaming.stackexchange.com/users/580/aranasaurus
Steam used to block all downloads as soon as you launched a game.
However, there is no need for a workaround anymore, thanks to the new content system: when you download a game, it is possible to launch and play a single player game under Steam and continue downloading others games in the meanwhile.
Fixed downloading new update while game is still running Reference: Steam client updates .
In addition, the new content system will allow us to build several new features that we’ve often heard requested.
Upcoming client releases will include things like download scheduling, bandwidth throttling, and prioritizing which games get downloaded first.
You’ll also be able to download an update to a game while you’re playing that game ; Steam will apply the update after you exit the game.
Reference: Steam news .
Some people are talking about downloads being suspended, but I have never experienced this problem.
I suggest choosing another server and trying again if this happens to you.
Apparently, a new feature is coming.
gaming.stackexchange.com/users/3921/Wok
While playing, hold Ctrl, Alt, and Del to go to pick a menu.
Pick the "Start Task Manager" then you can go to window.
Open steam then resume the downloading then click the picture where you were playing.
ENJOY!
gaming.stackexchange.com/users/11496/DaSniperShot113
After the game was started, you may also ALT-TAB back into steam, and then right-click and press "Pause Download" (even though it says "Paused" already), and then right-click and choose "Resume Download".
I have noticed that some games do not pause your downloads, but most games do.
gaming.stackexchange.com/users/19208/gameaddict
I have many games on Steam and many more I will buy, but I have a problem and I hope you can point me a solution.  When I download a game,  is it possible to launch and play a single player game under Steam and continue downloading others games in the meanwhile ?  Steam stops my download as soon as I launch any game, and I am looking for a way to prevent this.
How do I continue downloading a game in Steam while playing?
gaming.stackexchange.com
<steam>
gaming.stackexchange.com/questions/2857
gaming.stackexchange.com/users/730/Drake
In the Global Option, you can allow downloads during gameplay.  You can also ALT-TAB back into Steam and click "Resume Download". The official way is to change the global option in the downloads settings. There is also however a workaround, if you alt-tab out of the game and resume the download from there.
User suggests changing a global option. There is also a work-around suggested.