Steam is launching a new feature that allows offline local co-op games to be played online, but there's some limitations.
Introducing Remote Play Together, a new Steam mode lets you play local-only arcade-style games like Cuphead or Killer Queen Black with friends on the internet. It's a way for developers to extend playtime and reach for audiences on PC, and potentially make more sales. Valve says that all local co-op games will be automatically entered into Remote Play Together beta.
The logistics are quite similar to the PS4's Share Play functionality, which basically streams gameplay to another console via a connected network.
The host PC will basically handle the processing and rendering, and then stream the game to other machines, which will then send button presses and signals back to the host. Valve says this stream will be potent enough to deliver 1080p 60FPS, but gamers will need at least a 10Mbs connection at all times.
It might be possible for friends to play a game with you without actually owning it, similar to Sony's Share Play. Devs can opt out of the program if they disagree, but Valve says it's not going to let gamers use Remote Play Together to avoid buying a game.
The beta begins October 21 on Steam and you can get in by checking your settings.