GSM, UTF-8, Character limits … oh my!

Posted on Posted in Mogli SMS, Uncategorized

Say what?

Whether you know these terms like the back of your freckled hand, or have never heard of them before, you may not understand their relevance to SMS messaging. Put simply, these standards and character sets determine the number of characters that are sent within a single SMS message.

Most mobile networks use the GSM standard, which limits a standard text message to the GSM character set. Using GSM, a single SMS can contain up to 160 characters. However, the characters must be part of the so-called 7-bit default alphabet as specified by GSM 3.38 character set. Using any character that is not in this set requires the SMS to be treated as a Unicode SMS – which limits the length of the SMS to 70 characters due to the different character encoding.

 

Okay, then why can I send/receive messages with more than 160 characters from my phone?

Mobile networks are tricky and are typically able to take long messages that have more than the allotted number of characters, split them into multiple messages, and then concatenate the messages on the recipient’s mobile device. This concatenation process adds an additional 6 characters to each message for the concatenation string needed to rebuild the message.

 

If the recipient will still receive my message as I sent it, why should I care about character limits?

Simply put, going outside of your character limits will cost you more. You may not notice this on your personal messaging plan if you have unlimited messaging. However, if you are paying per message and every message you send is 170 GSM characters, then you’re effectively paying double for your 10 extra characters.

 

Ugh. That could add up. How do I avoid that?

  • There are a few easy steps you can take to avoid having your messages split.
    • Count your characters! You can do this manually or use the len function in excel to do this easily.
    • Avoid using MS word or similar word processing programs when composing an SMS message, as these programs typically use non-GSM characters. Instead use plain text editors or excel-type programs.
    • Use a third-party tool to check your message for length and use of non-GSM characters.
    • Swap the common characters below with GSM-friendly characters.

Remember, although you may be pressing the same keystroke for comma, apostrophe etc, character encoding actually depends on the text editor used, so double check!

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