What is a Segment?
In short, a segment is a portion of an SMS message. When a message is long or complex, it's broken up into multiple segments for the text carrier to send. It's important to be aware of how many segments your message contains for billing purposes.
What Segments Mean
Each segment contains 160 standard characters. For the purposes of understanding how this works, let’s imagine this segment of 160 characters is a box. If we fill this box with standard pebbles, we can fit 160 pebbles into this box. However, if we want to fill it with large rocks, we won’t be able to fit as many in.
In the SMS world, the standard pebbles are all standard characters, so we can fit 160 of these into our message segment. Standard characters are going to be your basic letters and characters – pretty much everything you can see on a keyboard. This character set uses the standard SMS encoding called GSM 03.38.
Alternatively, the big rocks are all non-standard characters, so we can’t fit as many. These include anything that uses a different type of encoding (other than the standard GSM 03.38). This includes emojis and some accented characters, which don't equal one character. With these characters, you have to use a completely different type of encoding called UCS2.
If we have a combination of big and standard rocks, we will fit as many as we can until it fills that box of 160 characters. Anything more will be send as an additional segment.
Additionally, when a message is split into segments, the third-party text service uses headers to tell the text carrier how to assemble the message in the proper order. This also takes up characters which is why 2 segments doesn't equal 320 characters.
You can use this tool to calculate how long your message will be. The Connect tool already includes the 17 characters 'Text Stop to End' that are required for compliance. Additionally, make sure to include your shortlink as well if you want an accurate count.
At the core, a segment is simply a count of characters (letters, symbols, numbers, etc.). SMS providers define the number of characters that make up a segment, as a way to store and send information of a specific size. In general a segment is 160 characters, but it is worth noting that certain characters are larger is size, because it takes more to store and send them. For example, emojis require more storage space and therefore result in more character space than a letter would.
SMS providers also bill for usage based on number of segments sent. Because they can control the size of a segment (and therefore how much it will take to store and pass on) they can create a standard pricing model based on segments. Connect usage is also billed on number of segments used, so it is important for clients to understand how segments are calculated. Every campaign message will show the number of segments that will be sent. This number is calculated based on the number of segments of the message itself and the number of customers it will be sent to. For example, if a message is 2 segments is sent to 100 customers, the total number of segments used is 200 (2 segments x 100 customers).
For more information about segments: https://www.twilio.com/blog/2017/03/what-the-heck-is-a-segment.html
MMS segments, or Multimedia Messaging Service, are different than traditional SMS segments. MMS segments are measured by total data size (maximum of 5MB) whereas segments are measured by character count. Because the images have to be sent as a single unit (as opposed to text segments that can be broken up if needed), it requires more data to send the larger unit. As such, MMS units cost more to send and are then billed to clients at a higher rate than regular SMS segments.
When a campaign is sent with an image uploaded, the entire message (including the image and any text) get sent as one MMS segment. This makes the usage and billing metrics very straightforward. If an MMS message is sent to 100 customers, the total number of MMS segments sent will be 100 (1 MMS unit x 100 customers).
For more information about MMS: https://www.twilio.com/docs/glossary/what-is-mms
What You Need to Know
The important thing to understand is that if you use a SINGLE non-US character, then the bytes required for all characters match the size of the largest character.
If you type: 'Hello Dog' that will be 9 characters and use up 9 bytes (of 140) in the segment because all of the characters are in the GSM7 character set.
If you type: 'Hello 🐶' that will be 7 characters but use up 28 bytes (of 140) in the segment because the 🐶 character requires using the UTF8 character set where each character (no matter what letter/symbol it is) requires 4 bytes.
If you include an image in your message (MMS), segments will be billed at a higher rate than regular SMS messaging. MMS is an add-on to Connect and will be enabled as such. If you're interested in using MMS, please contact your Client Services Advisor.
Just below the box where you type your message, you’ll see the segment count, so you'll know ahead of time how many segments your message is.
How Segments Look to Customers
Some carriers will still display a multi-segment message as separate messages. Others will display it as a single message 'bubble.' If the customer doesn't have unlimited text messaging, each segment goes towards their monthly message allotment. Smaller carriers like Sprint show each segment as an individual message while larger carriers like Verizon display it visually as 1 message although it's segmented on the backend.
Our third party text carrier, Twilio, has a helpful article here.
That’s pretty much all there is to understanding segments! If you have any further questions, feel free to reach us anytime by clicking on the help chat in the bottom left of your screen. We’re always happy to help!