Google has announced that Stadia players can now stream content at 1440p resolution – up from 1080p – provided they have the suitable hardware and internet connectivity at their disposal. You need to have a monitor with a screen resolution of 1440p or 4K, or a 4K TV with Chromecast Ultra plugged into it, in order to stream at such a high resolution.
Aside from having the right hardware, players must also have an active Stadia Pro subscription and must be hooked to a network with an average speed of 35Mbps or higher. But do keep in mind that cellular connectivity won’t cut it, and you’ll need a fairly stable Wi-Fi connection that can bear the cost of consuming an average 20GB of data per hour if you play games at 4K on Stadia.
You must also make sure that the Windows machine or Chromebook on which you are enjoying Stadia streaming at 1440p resolution should be capable of VP9 hardware decoding. Of course, with Stadia Pro, you also get perks such as 5.1 surround sound and High Dynamic Range (HDR) graphics.
Source: Stadia Community