You've likely encountered SMS messages, even if you didn't know it. Here's how they work—and why scammers love them.
What Is SMS? Your Guide to Text Messaging Basics
Updated on May 29, 2025
Trillions of text messages are sent and received via SMS-enabled devices every day, but have you ever stopped to ask, “What is SMS, exactly?” One of the oldest forms of mobile messaging, SMS messages are still among the primary ways many people communicate with loved ones, receive promotions from businesses and more.
“The average person won’t [notice or] care whether their phone sends a message as SMS,” says Thomas Reed, staff product manager at the cybersecurity company Huntress. But there is one good reason why you should: SMS messages can leave you and your information vulnerable to scammers.
That’s where this guide comes in. We’re answering your most pressing questions: What does SMS mean? What is SMS messaging? How does SMS work? And what’s the difference between SMS, MMS and RCS messages?
Keep reading for all that and more, including expert insight about how safe SMS is, how to stop spam texts and ways to steer clear of hackers.
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What is SMS?
SMS, which stands for short message service, is a form of text messaging that allows a message to travel across mobile phones using cellular networks almost instantly. It was created before cellular data existed, so each message can be no longer than 160 characters, Reed says. (If an SMS message is over the limit, your phone carrier will send it in multiple 160-character parts or convert it into an MMS message.)
These messages use protocols that were standardized in 1985 by the Global System for Mobile Communications (GSM), about a decade before the first text was sent. The very first SMS message was a “Merry Christmas” text sent on Dec. 3, 1992, by Neil Papworth, a test engineer for the SEMA group.
Since then, the messaging service has come a long way, catering to not just personal but even business communication (think: text-based ads and marketing). Statista reports that, due to its cost effectiveness and wide reach, ad spending for SMS advertising in the United States might hit $318.5 million by the end of 2025.
How does SMS work?
SMS messages are like digital postcards, following the path from sender to receiver through mobile network signalling channels.
Here’s how they work:
- You type out a message and the receiver’s number in your phone’s Messages app (on an iPhone or Android phone) and hit send.
- Your phone converts the message and contact number into transmissible data to send to a short message service center (SMSC). This is a central server location that functions like a post office, checking the recipient’s phone number to identify the right network to send the message to.
- The SMSC sends the message to the receiver’s mobile network.
- If the receiver’s device is available, the receiver’s network SMSC sends the message forward. Otherwise, the SMSC stores the message until the receiver’s phone is available.
- Once the receiver’s phone gets the message, it notifies them about the new text message.
- The device then connects to the SMSC to retrieve the message and displays it to the receiver.
How secure is SMS?
Since SMS messages don’t directly transmit from the sender to the receiver, they aren’t entirely secure with the end-to-end encryption that secure messaging apps provide.
But despite this obvious flaw, SMS is wildly popular with many platforms and businesses for two-factor authentication (2FA). This might sound familiar to you if you’ve ever forgotten a password. Using 2FA will allow you to seamlessly log in to any platform that supports it using your preset password and a one-time password (OTP) sent through an SMS message to your phone. In fact, 2FA is far more secure than using just a password and is easy to implement.
A word of caution: 2FA can be risky sometimes. If you ever lose your SIM card or phone, you might be at risk of losing a lot or all of your personal data since hackers today are skilled enough to intercept your SMS messages.
How do other messaging systems compare with SMS?
SMS texts aren’t the only format around. In fact, other messaging standards that provide better features are becoming more widespread. Read on to learn how they stack up.
MMS vs. SMS
Short for multimedia messaging service, MMS is a type of SMS text message that “allows for much larger messages, plus the inclusion of pictures, audio clips or videos,” Reed says. MMS messages don’t have a character limit, allowing users to send longer texts.
The only downside? Depending on your phone carrier, MMS messages might cost an additional fee. Nevertheless, MMS messages are popular with smartphone users.
RCS vs. SMS
Rich communication service (RCS) is a next-gen carrier-provided messaging service that works on Wi-Fi or mobile data. It allows text, high-resolution videos and photos, links and more to be shared between users while providing features like typing indicators as well as delivery and read receipts. It’s also a great way for businesses to ensure customer engagement since it allows them to send messages with action buttons that can elicit responses—for say, appointment bookings—from the receiver’s end.
One major way in which RCS differs from SMS is that it doesn’t have a character limit. And although it doesn’t provide end-to-end encryption like iMessage, it supports partial encryption and is more secure than SMS. Businesses can also verify their identities, reducing the likelihood of phishing attacks and spam.
Who uses SMS, MMS and RCS?
RCS is the default messaging type on Android devices, a modern standard that most Android users rely on instead of SMS and MMS. The system is relatively new on iPhones, so while some use RCS by default, others—including those running systems earlier than iOS 18—use the internet-based iMessage system.
Secure messaging apps like WhatsApp and Signal also use their own internet-based systems rather than SMS or MMS.
That said, when iPhone users can’t connect to the internet or when they send text messages to recipients with Android devices, their iPhones will use SMS or MMS instead. Apple users can literally see the difference between the message types on their screens: SMS messages are green, while iMessages are gray or blue.
SMS messages are also used extensively by businesses for everything from marketing to customer service. They work great to keep interactions with customers going, provide important information (whether product updates or delivery details) and promote products and services.
On the other hand, scammers are also more likely to use SMS or MMS messages because they are less secure, according to Reed. “Spam texts [via SMS or MMS] are unfortunately not only possible but relatively easy, not just to send but also to spoof,” he says, referencing a scam in which fraudsters disguise their phone number to make you believe they’re someone else. “You cannot trust that the number your phone says a text came from is actually the number it came from.”
Before clicking on any links in a message or sharing personal information via text, Reed recommends calling the sender directly to confirm that the message is real.
How much do SMS texts cost?
While SMS text messages are free for users with unlimited texting phone plans, mobile carriers charge customers who don’t have unlimited texting or who send SMS messages outside of covered areas.
Most carriers charge the same rate for both SMS and MMS messages. For example, T-Mobile charges 50 cents per text, while Verizon charges 20 cents per text. AT&T users, on the other hand, must pay extra for MMS vs. SMS messages, at a rate of 20 cents per SMS message and 30 cents per MMS message.
SMS continues to remain relevant today, especially for businesses and organizations, thanks to staggering open rates of 98% and cost-effectiveness. Although newer messaging platforms have become popular, SMS is supported by almost every mobile and network provider, which makes it possible to reach a larger audience a lot more easily.
Why trust us
Reader’s Digest has published hundreds of articles on personal technology, arming readers with the knowledge to protect themselves against cybersecurity threats and internet scams as well as revealing the best tips, tricks and shortcuts for computers, cellphones, apps, texting, social media and more. For this piece on what SMS is, Brooke Nelson Alexander tapped her experience as a tech and cybersecurity writer to ensure that all information is accurate and offers the best possible advice to readers. We rely on credentialed experts with personal experience and know-how as well as primary sources including tech companies, professional organizations and academic institutions. We verify all facts and data and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.
Sources:
- Thomas Reed, staff product manager at Huntress
- Statista: “Total number of SMS and MMS messages sent in the United States from 2005 to 2021”
- Statista: “SMS Advertising – United States”
- Forbes: “Is SMS Marketing An Affordable Small Business Growth Booster?”
- Apple: “What is the difference between iMessage, RCS, and SMS/MMS?”
- Wired: “A Guide to RCS, Why Apple’s Adopting It, and How It Makes Texting Better”
