When a message on an Android device is indicated as being “sent as SMS,” it signifies that the message was transmitted using the Short Message Service protocol, rather than over a data connection like Wi-Fi or cellular data. This typically occurs when the recipient does not have Rich Communication Services (RCS) enabled, or when the sending device cannot establish a data connection. For instance, if a user sends a message to a contact, and the message bubble turns green instead of blue, it indicates the message was delivered via SMS.
The utilization of SMS for messaging offers the advantage of broad compatibility, as it is a universal feature on virtually all mobile phones. This ensures that messages can be delivered to individuals regardless of their device’s capabilities or data connectivity. However, SMS lacks the advanced features associated with data-based messaging, such as high-resolution media sharing, read receipts, typing indicators, and group chat enhancements. Historically, SMS was the primary method for text-based communication on mobile phones, predating the widespread adoption of data-driven messaging applications.