Although, recent Universal Profile specifications allow that to be decoupled, relying instead on an OpenID. And worse, it's all tied to a phone number. But it's not a great experience, with an awkward setup process, single-device support, and no real native experience since it's a web app. On PC, the closest thing we have is Messages for web. All the carriers gave up and have since left it in Google's hands, abandoning their half-baked, too-late joint venture. No one wanted a single, centralized solution under one company's control, but it's the answer we got when the children at AT&T, T-Mobile, and Verizon refused to play nice with each other. Google's Chat is the company's take on a Universal Profile RCS system, ripped away from the carriers who had nearly a decade to get it right and refused to. If these separate systems do things right, even if customers are on separate servers, they're all part of the same network.

It isn't required by the Universal Profile spec, as far as we can tell, but it's the version that makes that easiest. Networks still need to build in that interoperability. A good Universal Profile implementation means these distributed systems can intercommunicate, so a message sent on a Random North American Carrier can be received by Destination Japanese Carrier. RCS can work in a decentralized manner, allowing carriers and companies to spin up their separate servers that don't talk to each other.

Most importantly, it encourages interoperability. It's the best version with the most beneficial features implemented to a specific set of agreed-upon standards. There are several RCS implementations (the carriers tried and failed to spin up their garbage, locked-in versions), but the most important one to know about is the Universal Profile.

Use imessage on android