Interoperability is the property that lets an RCS message sent on one carrier or device arrive, with its features intact, on another. It is what the GSMA's Universal Profile exists to guarantee: a single specification of the features, formats and network behaviour every RCS implementation supports, so that a rich card or a read receipt means the same thing on AT&T as on T-Mobile, and on a Samsung as on an iPhone.
Why it was the hard part
Early RCS was fragmented. Carriers launched their own versions, features differed, and a message between networks often lost its richness or fell to SMS. The Universal Profile fixed the specification, and Google's Jibe platform fixed much of the deployment by hosting RCS for most carriers on one backend, so that cross-carrier delivery became the ordinary case rather than the exception. Apple's adoption of the Universal Profile in iOS 18 closed the last large gap in the United States.
What it means for a business
Interoperability is why one verified agent reaches customers across every participating carrier, and why the same message format renders consistently. Where a handset or carrier still cannot take RCS, fallback to SMS covers the gap. Which carriers support RCS tracks the current state.
Still to watch
Feature parity is not perfect across versions of the profile, so the newest capabilities can lag on some devices, and cross-border interoperability remains uneven. A business sending in the United States sees very little of that.