Three standards behind the “text”
The phrase “text message” covers three different systems that share one inbox on most phones. SMS is the oldest and simplest, MMS extends it to media, and RCS is a newer standard intended to bring app-like features to the default messaging app. Which one carries a given message depends on the phones, the carriers and the settings involved, and the app usually chooses automatically.
SMS: the original
SMS stands for Short Message Service. It dates from the early days of mobile networks and was designed to be small and dependable. An SMS message travels through the mobile carrier’s signalling system rather than as ordinary internet data, which is why it can work on a phone with a weak signal and no data connection.
Key properties:
- Plain text only, with no images or video.
- A short limit. A single message is commonly capped at 160 characters in the basic character set, and fewer when special characters or emoji are involved. Longer texts are usually split into parts and reassembled by the receiving phone.
- Phone-number based. You need the recipient’s number, but no particular app.
- No built-in protection. SMS is not end-to-end encrypted, and carriers can generally see the content.
- Basic features. There are no standard typing indicators, and delivery reports are limited.
Because of this simplicity, SMS works almost everywhere, which is why many services still use it to send verification codes. For sign-ins, the convenience comes with limits, and some people prefer passkey sign-in or an authenticator app where available.
MMS: adding pictures
MMS stands for Multimedia Messaging Service. It lets a text message carry photos, short audio or video clips and longer text. It uses mobile data, so it can fail if data is off or the signal is poor.
MMS has a size limit set by carriers. The exact figure differs between carriers and regions, so it is best not to rely on a specific number. To stay within limits, phones often compress images and video heavily before sending. This is why photos sent by MMS can arrive looking soft or blocky compared with the original.
MMS is also what many phones use for group texts when some participants are on different platforms. Group MMS can be unreliable: replies may go to the wrong people, members cannot always leave and the conversation may split into separate threads.
RCS: the modern upgrade
RCS stands for Rich Communication Services. It is a standard from the mobile industry, meant to replace SMS and MMS in the default messaging app. Instead of the carrier’s signalling system, it sends messages over a data connection, either mobile data or Wi-Fi.
Features RCS typically allows include:
- Typing indicators and read receipts
- Higher-quality photos and larger files than MMS
- Better group chats, with named groups and the ability to add or remove members
- Messaging over Wi-Fi
- Business messages with buttons or verified sender branding, depending on the carrier and app
The exact feature set depends on the version of the standard supported and on the messaging app. If RCS is unavailable between two phones, the app generally falls back to SMS or MMS, and the richer features disappear.
Why compatibility is patchy
RCS support has been uneven. Android phones using Google’s messaging app have supported it for some time, and many carriers support it as well. Apple added support in newer versions of its software, so conversations between iPhone and Android users can use it where both sides and the carrier support it. Availability varies by country and carrier, so a feature you see on one phone may not appear on another.
Encryption is another uneven area. RCS conversations are protected in transit, but whether a conversation is end-to-end encrypted has depended on the apps and the version of the standard involved. The industry has worked on adding end-to-end encryption between different platforms, but you should check the current status for your own phones rather than assuming. The earlier description of what end-to-end encryption covers and leaves exposed applies equally to texting.
Chat apps like WhatsApp, Signal or iMessage are separate from these standards. They run over the internet on their own servers and generally only connect users of the same app. They are not part of SMS, MMS or RCS, although they sit in the same place in daily life.
What the colours and labels mean
Some phones show different bubble colours or labels depending on the kind of message. On certain platforms, one colour indicates a message sent through that company’s own app, and another indicates standard texting. The labels mostly tell you which system carried the message and, therefore, which features you can expect. If you see a message marked as “text message” or “SMS”, it is likely using the older, more limited route.
Practical differences you may notice
- Blurry photos. Often MMS compression. Sending the photo through a chat app, a link from cloud storage or email can preserve more quality.
- No read receipt. Standard SMS does not provide one, and RCS receipts depend on the settings of both people.
- Messages not sending on Wi-Fi. SMS and MMS traditionally need a cellular connection, whereas RCS can work over Wi-Fi. Some carriers also support Wi-Fi calling and texting.
- Group text chaos. Mixed groups with different platforms or standards often fall back to MMS behaviour.
- Cost. Many plans include unlimited texts, but some charge for messages, particularly when travelling or sending to other countries. Check your plan. Moving to a new handset or an eSIM plans arrangement can also change how texting is set up.
- Delivery failure. If RCS is switched on and the other person’s phone cannot receive it, messages may be delayed. Turning RCS off temporarily or waiting for fallback can resolve this.
Staying careful
Texts from unknown numbers can be scams, and the fact that a message arrives in your normal inbox does not prove it is genuine. Fake parcel or bank notices are common and are covered under smishing attacks. Do not tap links in unexpected texts, and do not share verification codes with anyone who contacts you.
For private or sensitive conversations, consider whether a standard text is the right channel, since SMS offers little protection. For casual use, SMS, MMS and RCS together are convenient because they work with almost anyone who has a phone number.