Is there a way to alt-tab out of Minecraft (i.e. make Minecraft lose focus) without the game auto-pausing and without having to bring a menu (e.g. inventory) up first?
For single player, it seems that you’ve already figured out that bringing up the inventory screen prevents the game from auto-pausing when it loses focus. I don’t believe there is any other way to prevent the auto pausing.
You may, however, consider hosting a SMP server and being the only person connected to it. In SMP, the game will not pause when you are alt-tabbed out. You can install mods on a SMP server that allow you to create user whitelists to define who you want to connect to your server. If you add only yourself to that list, you don’t need to worry about anyone else connecting while you are playing.
Source : Link , Question Author : Brian Beckett , Answer Author : Dave McClelland