In this article we’ll pull back the covers on how SMS messaging works and the technology behind it. Here’s what we’ll cover...
- Understanding what a segment is
- Encoding standards and headers you use to send messages
- Crafting the perfect message
- Subtle gotchas & pro-tips
What Old, T9 Texting Can Teach Us About Message Segments
Remember when you used to text on a blackberry or a Razor? Maybe you had the infamous Nokia. Regardless, texting was typically done on a T9 keyboard and in the top right corner of the message box you could see a counter. Before you started typing it looked like this: 160/1. The first number in the ratio was counting how many characters you had left per segment and the second one was counting how many segments you had used. As you typed, this counter would keep track of your characters and the 160 would count down. If you hit 0, that would start you back over and you’d see it change to a 2, looking like this: 160/2.
This signaled to you that the message was going to send as two messages. This was mostly important because there was no such thing as unlimited text messages, and you knew you were going to be charged for two messages.
Can you see that faint little counter in the top right across from the word “Message:”? Takes you back, doesn’t it?
Has Anything Changed With Message Segments?
Honestly, SMS standards have barely changed since the early 2000s. New things like iMessage, Facebook Messenger and What’sApp have introduced a new way to message. These methods seem like text messages but they are very different and all involve sending messages through the internet.
Here at Text In Church, we send true SMS text messages that travel through cell signals, not the internet. This means the recipient of your text message doesn’t have to have data on their mobile phone to receive your messages.
But SMS messages are still structured the same way they were when they were created in the 80’s. They are sent in 140 byte chunks known as message segments.
Text In Church sends your messages one segment at a time. To figure out how many characters this affords you, we’re going to have to do a little math.
Let’s Do Some Calculating...
Standard SMS encoding uses the GSM character set which takes 7 bits to encode a character. 140 bytes x 8 bits in a byte divided by 7 bits to encode leaves us with the 160 character message segment. So, that’s where that 160 character limit came from.
Message segments are how Text In Church (and the SMS industry as a whole) counts messages.
Does that make sense?
Understanding How to Craft the Most “Compliant” Message
You’re in Text In Church about to send out a message to your first time guests about an event coming up. You’ve written the perfect message that is under that 160 character limit and even has a nice emoji; however, something doesn’t seem right.
Part of the answer lies in the encoding. Since this message has been limited to 67 characters per segment, that means this message is being sent using UCS2 encoding instead of GSM. To accommodate a message with this type of text, Text In Church has to use a different character set. When you send messages with non-GSM characters such as Emojis, we have to use a different type of encoding known as UCS-2. UCS2 takes 16 bits to encode each character. So, going back to the math we did above, we now have a limit of 70 characters (140 bytes * 8 bits in a byte / 16 bits).
Besides emojis, you should also be careful with accented characters. GSM includes some accented characters such as ñ, à, and ö, but does not include others such as á, í, or ú. These will all impact that character count.
Okay… But why is my message at a 67 character limit and not 70? The last piece of the puzzle lies in concatenation. When you send multi-segment messages, Text In Church uses User Data Headers to tell the destination how to reassemble it. This takes up 6 bytes per message, leaving only 67 characters for UCS2 encoded messages or 153 for GSM encoded messages.
So, maybe you decide the emoji isn’t worth it after all. However, when you trim the same message down, it still doesn’t seem to work out quite right:
This message contains a “gotcha” that commonly causes encoding issues: a smart apostrophe. You see, I copied and pasted this from a Google Doc. When that happened, it brought over hidden formatting that was outside the GSM character set. It’s always best to type out your message in our message builder.
There! I fixed my text message. I typed it out fully in the box and kept it under 160 characters. It will now send with the highest deliverability rate and, thus, get the most engagement.
Keep in mind that it’s always best to keep your text messages the size of one segment. Carriers aggressively filter messages that go over 1 segment and that can cause a drop in engagement.
After reading this article you’re fully equipped to make decisions about whether Emojis are worth it, you know not to copy and paste text into the message body, and how accurately count up segments before you send out your message instead of after. I know it was a long, techy road to get here, but doesn’t that feel empowering?!