Game streaming relies on low-latency connections to offsite servers, which is why the key to a great experience with Xbox Game Streaming and Google Stadia is fast and reliable internet. Google began testing mobile data streaming with Stadia in July, and now the functionality is ready for everyone.
Playing Stadia over a cellular connection currently requires tapping your icon in the Stadia app, selecting the Experiments menu, and enabling 'Use Mobile Data.' Google has now updated a support page about the mobile data feature, removing all references to it being an experiment. You still have to enable it manually, but Google has seemingly worked out all the kinks.
Google still warns that mobile streaming uses a lot of data. "Playing games on Stadia may use a significant amount of data," the company says in a support article. "If you enable the Use mobile data option on your mobile device, it is strongly recommended that you track your data usage to avoid unexpected data charges."
- Google Support