Steam Cloud Play has been made public by Valve, at least to development partners. We previously reported on the possibility of a Steam cloud gaming feature and it looks like it's finally happening, though it won't be its own service. It'll serve as a bridge between Steam and NVIDIA's GeForce NOW, for example, which is the first to be supported by Steam Cloud Play although more may be added in the future.
Steam Cloud Play is currently in Beta and features are being added over time. We are now accepting a limited amount of games into the service as we continue to build features and server capacity for players. The first service we are connecting to Steam to allow users to play games from their Steam Library from the Cloud is Nvidia GeForce NOW. There are more details below about how to opt your game(s) into the service as well as answers to a few common questions below.
Currently Nvidia GeForce NOW is available in North America, Western Europe and Asia Pacific. Currently, Steam users will need to download the GeForce Now client and connect their Steam account to the GFN service to play their Steam Library. The user may pay a subscription cost to use the GFN service. Customers will continue to acquire games on Steam the same way they do today, and partner payouts will remain the same.
These cloud services enable Steam users to play their Steam library in the cloud, one game at a time, like they can on their local PC. Developers must manually opt-in the games they wish to make available on GeForce NOW.
Will there be other cloud gaming services added to Steam Cloud Play?
We may add additional Steam Cloud Gaming services in the future. At that time we would reach out to you to opt your games into the new service.