RCS vs. SMS: What's the difference?

What is SMS and how does it work?

SMS does not use IP, nor does it require Wi-Fi or LTE/5G cellular access. Instead, SMS communications are sent directly through the cellular network, like voice calls. SMS relies on the Global System for Mobile Communications protocol that defines how messages are sent and received over the carrier's network.

For intercarrier communications, the Short Message Peer-to-Peer protocol helps with delivery between carriers. The use of the cellular network, as opposed to internet communication, is why messages sent and received using SMS don't count against mobile carrier data plans.

By contrast, RCS and messaging platforms, such as WhatsApp and Facebook Messenger, are IP-based and use the internet for transport. These types of apps are known as over-the-top (OTT) messaging apps and use the mobile user's IP data plan to send and receive communications.

An upgrade to SMS, called Multimedia Messaging Service, accommodates the transmission of images, audio and video. MMS uses the same protocols and transport methods as SMS. In addition, MMS per-message payload caps are set much higher to accommodate the larger file sizes associated with multimedia content. MMS is beneficial in situations where cellular voice access is available but IP-based services are not.

What is RCS and how does it work?

Compared to SMS, RCS is a newer messaging protocol. Mobile carriers are shifting away from traditional SMS and toward RCS to better compete with the popularity of OTT communication apps.

The concept and benefits of RCS are simple: The protocol provides the same feature-rich communication features found in the most popular IP-based communications services. These advanced features include group chat, delivery of high-quality photos or videos, read receipts and location sharing.

RCS is an open standard, meaning any device can incorporate the feature-rich protocol at no cost and with no concern about inoperability. Devices sending and receiving RCS messages must be connected to either Wi-Fi or LTE/5G IP data network services. Data sent and received counts against any mobile carrier data plans in place.

Compare RCS vs. SMS

RCS and SMS are quite different in terms of network dependency, functionality, message delivery and confirmation, integrations and security:

• Network dependency. A key difference between RCS and SMS is that SMS sends messages over the cellular network, while RCS content requires data connectivity before it can be transmitted. In some situations where data connectivity is not available, it's still possible to send and receive SMS-supported messages. With the expansion of LTE and 5G, however, internet connectivity is plentiful in most areas, enabling a feature-rich service.
• Functionality. SMS has a strict character limit of 160 and no support for multimedia capabilities within messages. RCS supports a range of multimedia within messages, including video, GIFs and audio. RCS has no character limit, and messages can be sent from one to many for group chat capabilities. Additionally, files can be transferred directly over the service.
• Message delivery and confirmation. SMS has few message delivery confirmation capabilities that largely depend on the carrier's settings. In most cases, SMS only notifies the sending user that the message was successfully delivered. RCS, on the other hand, uses more advanced messaging features that more precisely inform senders that messages were delivered and if they've been read.
• Integrations. Because SMS uses the carrier cellular network for the transport of messages, integrations with other applications and services are limited. However, since RCS uses IP like most other mobile applications, it offers greater potential for integration with other messaging services, chatbots and business tools, such as CRM systems, sales and marketing automation platforms, and ticketing services.
• Security. SMS messages offer no encryption, opening the door to message interception, tampering and an overall lack of confidentiality. RCS adds security components, such as Transport Layer Security for encryption while messages are in transport and Secure Real-time Transport Protocol for voice/video delivery. However, some third-party applications that use RCS may use additional or different data encryption methods to ensure end-to-end encryption.

Because of these differences, RCS is considered a more convenient and feature-rich communications platform when compared to SMS and even other OTT counterparts, like WhatsApp, Facebook Messenger and Telegram. These third-party services require the sender and receiver to be logged in to use the same app. RCS offers similar security functionality to third-party services, such as message encryption and verifying messages before they're delivered. SMS does not support these security features.

How to use RCS and what devices support it

The availability and capabilities of RCS depend on two factors. First is support by the carrier, and second is the implementation model the provider chose to implement. Depending on what the carrier has decided to implement and support, some RCS features may not be available.

RCS has been available through major U.S. carriers for many years, and global carriers have been working diligently to support the protocol as well. However, RCS functionality is not necessarily enabled by default on all mobile phones.

For example, smartphones running Android 5.0 and higher can access RCS, and users can enable or disable RCS chats within their settings. If the phone manufacturer uses the Google Messages app, RCS features are often enabled by default. However, it's best to verify whether RCS is truly enabled by checking the application's settings.

Much of the slower-than-anticipated adoption rate of RCS was largely due to Apple's reluctance to implement it within its mobile OS. However, as of the release of iOS 18, Apple now supports RCS, and Apple-to-Android device messaging communications can now use these rich messaging features. This change by Apple will likely be the catalyst that sparks widespread adoption of RCS globally.

Editor's note: This article was updated to expand the comparison of RCS and SMS features and revise out-of-date information. We have also improved the reader experience as of December 2024.

Andrew Froehlich is founder of InfraMomentum, an enterprise IT research and analyst firm, and president of West Gate Networks, an IT consulting company. He has been involved in enterprise IT for more than 20 years.