The GSM 03.38 character set (definitely a technical term, bear with me) is the most commonly used encoding method when sending messages. It is a 7-bit alphabet, limiting 7-bit encoding to 160 characters. This means only specific characters can be used to achieve the maximum length of content.
Compared to the GSM character set, Unicode (UCS-2) encoding supports a much greater range of characters and languages, thus providing more options for content. So, if a message contains any characters not listed in the 7-bit alphabet, UCS-2 encoding is the default, and message length is reduced to 70 characters. To put it into perspective: If any of the characters used in a message that is not present in the 7-bit alphabet, the maximum length of one SMS messages becomes 70 characters, not 160.
Further, if a message exceeds 160 characters under GSM encoding, or 70 characters under UCS-2 encoding, an SMS is forced to be split, sending texts to the handset separately, with each SMS charged separately. Also note that the character limit per text in a multipart SMS is smaller –153 for 7-bit encoding and 67 for UCS-2.
So how can this break the budget. Let’s say a campaign is created to send messages to 3,000 people, and the SMS template calls for 155 characters, well within the limit of a single 7-bit message. But one of the characters in the message happens to fall out of the 7-bit alphabet, so the entire message is encoded using UCS-2. Suddenly what was expected to be 3,000 messages becomes 9,000 messages. Most importantly, 9,000 messages are charged to the account. This can happen in instances when a language specific letter is used, such as “ñ,” or even when using a different type of space.
To help avoid budget breakers, Messente developed the following two tools:
- The SMS Length Calculator - Check the message content for characters used, the estimated message length, and ways to optimize campaigns.
- The Auto Replace – Messente’s software automatically replaces Unicode characters with similar GSM-friendly characters.