What is RCS and how is it different from SMS and iMessage?

For years, the iPhone’s two-tiered texting system has been a hot topic. iPhone-to-iPhone texts in the Messages app are blue, and enjoy full encryption and more robust media features, like animations. But messages to and from Android devices are merely standard SMS texts, and marked with a green tint. Apple’s segregated messaging platform has been the subject of a , and even sparked chatter of regulatory intervention. But with Apple’s recent confirmation that it will begin supporting the newer RCS texting standard in iOS 18, is the iPhone messaging playing field about to be leveled? Or are we just exchanging one acronym for another?

Confused? Don’t worry. We’re about to lay out what could change with Apple’s adoption of the GSMA’s next-generation messaging protocol.

What is SMS?

Short Message Service (SMS) is one of the most ubiquitous messaging protocols on the planet. It dates back to the early days of mobile technology. In December 1992, Neil Papworth, at the time an engineer at Vodafone, sent the first SMS text message when he wished his boss “Merry Christmas.” By the start of 2011, approximately 80 percent of all mobile phone users globally — an estimated 3.5 billion people — were sending SMS messages every month.

Today, however, the standard has some notable drawbacks. SMS messages are limited to 160 characters, and texts you send can’t include photos, videos, audio or GIFs. For that, cell phones have long turned to a supporting protocol known as Multimedia Messaging Service (MMS), but it too has its share of technical limitations, including woefully small message size limits. SMS also doesn’t support end-to-end encryption.

But for all the ways SMS feels dated in an era dominated by instant messaging platforms, it has one defining advantage: SMS messages are routed through your carrier’s mobile network, meaning a data plan isn’t necessary to use the technology. That fact has meant SMS has often served as a fallback for more advanced protocols, including Apple’s iMessage.

What is RCS?

RCS is short for Rich Communication Services, though sometimes it is also marketed as “Advanced Messaging.” Either way, it’s often positioned as a next-generation replacement for SMS and MMS. RCS allows users to take advantage of many features that were previously exclusive to over-the-top messaging platforms like WhatsApp.

For instance, the RCS Universal Profile includes full support for read receipts and typing indicators. It can also facilitate proper group chats, and allow users to send high-resolution images, video and audio clips. As of earlier this year, Google’s implementation of RCS also offers by default end-to-end encryption (E2EE) for both one-on-one and group chats.

Unlike SMS texts, RCS messages are routed over a mobile data connection or Wi-Fi link, with SMS functioning as a fallback. For that reason, the older protocol likely isn’t going anywhere anytime soon.

One thing that’s important to remember about RCS is that it is not and has never been envisioned as a replacement or competitor to instant messaging apps. At its heart, RCS is a communication protocol between mobile telephone carriers and between a phone and carrier. Taking advantage of RCS does not require signing up for a new service. As long as your phone and carrier support RCS, and you’re using a compatible app such as Messages by Google, you can take advantage of everything the protocol has to offer — provided, of course, the person or people you’re messaging meet those same requirements.

How does iMessage fit into all this?

Apple announced iMessage in June 2011, a few short months before Steve Jobs died later that same year. Unlike RCS, iMessage is a proprietary messaging protocol controlled exclusively by Apple and available (barring some occasional, unofficial workarounds) only on iPhone, iPad, Apple Watch and Mac devices. Starting in 2024 with the iOS 18 update, Apple plans to integrate support for RCS in its Messages app. As of writing this article, the two protocols do not communicate with one another. As such, Apple’s Messages app will default to SMS/MMS when users attempt to send texts and media files to someone with an Android phone.

From the perspective of an iMessage user, it can feel like Android users are stuck in a bygone messaging era — even though the latter is not at fault for the situation. Due to iMessage’s reliance on SMS/MMS for Android communication, media files end up pixelated, there aren’t any read receipts or typing indicators and forget about trying to involve multiple iPhone and Android users in a single group chat.

How did we get here?

Although work on RCS began before Apple announced iMessage, the protocol had one major disadvantage that doomed it to a slow rollout. RCS is a multi-stakeholder project that includes the involvement of the GSMA, a trade body that represents the interests of the mobile communications industry at large. In 2015, Google took a more active role in the proliferation of RCS when it acquired Jibe Mobile. With Jibe’s technology as a base, it’s effectively Google that provides the glue that binds the RCS ecosystem together, but for a long time, the company did a poor job of aligning everyone involved in RCS toward a shared goal.

In fact, the early days of RCS were marked by false starts, with some carriers, including a group made up of AT&T, T-Mobile and Verizon forming a short-lived joint venture to push the protocol forward before eventually aligning themselves with Google. Even Samsung did its own thing for a while before it too eventually agreed to make Messages by Google the default messaging app it ships on phones in the US.

For that reason, Apple has had little reason to adopt RCS. After all, why would it give a bumbling competitor a freebie? And as recently as 2022, it seemed there was little to no chance the situation was going to change anytime soon. “I don’t hear our users asking that we put a lot of energy into that,” Apple CEO Tim Cook told the Code Conference that year when he was asked about RCS messaging. “Buy your mom an iPhone” was his final word on the matter.

But it was also last year that the European Union passed its landmark Digital Markets and Services Act (DMA). The legislation requires “gatekeepers” to not favor their own systems or limit third parties from interoperating within them. Gatekeepers are any company that meets specific financial and usage qualifications. Apple, according to the law, is one such company.

Ultimately, the EU ruled in 2024 that (though European regulators had plenty of other directives for other aspects of Apple’s empire). Despite being in compliance, however, Apple had . Per noted Apple pundit John Gruber, Apple’s bigger motivation may have been to . But whatever the reason, it appears to be a done deal: Apple reaffirmed RCS support is coming to the iPhone as part of iOS 18.

Does Apple’s support of RCS mean the end of green text bubbles on iPhone?

Alas, green bubbles are likely here to stay. The company noted in its original comment on RCS that iMessage “will continue to be the best and most secure messaging experience for Apple users.” That said, even if you take that statement to mean iMessage will continue to display texts from non-Apple devices differently from those sent from an iPhone, iPad or Mac, Apple’s adoption of RCS should lead to a better user experience for both iOS and Android users.

Again, Apple needs to provide specifics, but it’s easy to envision a future where its Messages app, thanks to RCS, properly displays high-resolution images and videos sent from Android phones, and allows both iOS and Android users to take part in group chats without something breaking. Apple also said in its original November 2023 announcement it would work with GSMA members to improve the existing Universal Profile protocol, with a focus on adding end-to-end encryption to the standard.

Of course, whether that interoperability ends the stigma around green bubbles is harder to answer.

Editors’ note: This story was originally published in November 2023 and has been updated to reflect new information.