Your phone quietly chooses between three different technologies every time you send a message, and the choice changes what the message costs, how it is delivered, and whether your recipients end up in a shared thread.
The three, briefly
| SMS | MMS | RCS | |
|---|---|---|---|
| Carries | Text only | Text, images, video, group threads | Text, media, typing indicators, read receipts |
| Length | 160 characters per part | Effectively unlimited text | Unlimited |
| Travels over | Carrier signalling network | Carrier data | Internet |
| Needs a data connection | No | Yes | Yes |
| Group threads | No — separate messages | Yes | Yes |
| Typical cost | Per message on your plan | Often costs more than SMS | Free (uses data) |
| Delivery reliability | Very high | Good | Depends on both sides |
SMS is the oldest and the most dependable. It works with no internet connection, on any phone made in the last thirty years, and it is what a message falls back to when everything else fails. It has no concept of a group: sending to ten people means ten separate messages.
MMS was added to carry pictures, and along the way it became the mechanism for group threads. When your phone puts several recipients in one conversation, it is sending an MMS. This is why an ordinary text “becomes an MMS” the moment you add a second recipient to the thread — and on many plans, MMS is billed differently from SMS.
RCS is the modern successor, effectively a messaging app running over the internet but built into the phone’s default messaging. Google pushed it for years on Android; Apple added support in iOS 18, which is why iPhone-to-Android messaging improved noticeably. RCS gives you read receipts, typing indicators, high-quality images and proper group threads — when both ends support it. When they do not, it silently falls back to SMS or MMS.
What this means for mass texting
Three practical consequences.
Long messages get split. SMS carries 160 characters, or 70 if your text contains any non-GSM character. Longer messages are split into parts and reassembled on arrival — and many plans charge per part. A 300-character message is two messages, and to 200 people that is 400. Worth knowing before you write a long one.
One accented character can double your cost. The GSM alphabet covers plain Latin letters and a handful of symbols. An emoji, a curly quote, or in some encodings an accented letter, switches the whole message to a 16-bit encoding where the limit drops from 160 to 70 characters. A message that fitted in one part becomes three. If you write in Italian, French or Spanish, this is not a corner case — it is most messages.
Individual messages are SMS; shared threads are MMS. Which loops back to the choice in group text versus individual texts. Sending 60 separate texts is 60 SMS. Putting 60 people in one thread is an MMS, and everyone sees everyone.
Green and blue bubbles
On iPhone: blue is iMessage, Apple’s own service, sent over the internet and free. Green is SMS or MMS, going through your carrier and counting against your plan.
If you are sending to a mixed list of iPhone and Android users — which any real customer list is — some messages go as iMessage and some as SMS. You cannot control which, and the practical implication is that your plan’s SMS allowance is consumed only by part of the list.
Does it still make sense to use SMS at all?
Given that WhatsApp and RCS exist, a fair question. SMS keeps two advantages that matter for announcements:
It arrives. No app required, no account, no internet connection, no friend request. If you have a working phone number, you get the message. Open rates for SMS remain far above email precisely because there is no inbox to compete with.
It reaches everyone. Your list contains people who do not use WhatsApp, older phones, and customers who gave you a number and nothing else. SMS is the only channel that covers all of them.
The cost is real, though, which is why the encoding details above are worth a minute of your attention before sending to a few hundred people.
Questions people ask
Why did my group text become an MMS?
Because a shared thread with several recipients is delivered as group MMS. That is how the group mechanism works — SMS has no concept of a group.
Why do some of my messages count as two or three?
Because they exceed the per-message character limit: 160 for plain Latin text, 70 if any character falls outside the GSM alphabet. Emoji and some accented characters trigger the lower limit for the whole message.
Does RCS work between iPhone and Android?
Since iOS 18, yes, when both devices and carriers support it. Before that, iPhone-to-Android fell back to SMS/MMS, which is the origin of the green bubble complaints.
Is MMS more expensive than SMS?
On many plans, yes — MMS is frequently billed separately or at a higher rate, and it consumes data. Check your plan before sending pictures to a large list.
Should I avoid emoji in a mass text?
If cost matters, yes. A single emoji switches the message to 16-bit encoding and drops the limit from 160 characters to 70, which can turn one message per recipient into three.