In this article, you will learn why some SMS messages in a serial message like a dunning run are charged differently. We will explain how the encoding format of your SMS messages impacts the cost, depending on the types of characters you use in the content.
Topics covered:
- SMS Encoding Formats
- Character Limits in GSM7 and Unicode
- Special Characters that impact SMS costs
- Impact on SMS Costs
Fast lane
- Check the content of your SMS messages.
- Ensure you are aware of the characters used (special characters, emojis, etc.).
- Know that different characters may trigger different encoding formats (GSM7 vs Unicode).
- Recognize that Unicode messages have a smaller character limit, leading to higher costs.
SMS Encoding Formats
When sending SMS messages, the encoding format used can vary depending on the characters included in the message. There are currently two common encoding standards: GSM7 and Unicode. Most SMS messages use GSM7 by default, but if special characters, emojis, or certain symbols are included, the system will switch to Unicode, which impacts the character limit and, consequently, the cost.
Character Limits in GSM7 and Unicode
Each encoding format has a different character limit per SMS message. With GSM7, the character limit is 160 characters for a single message. When sending a multipart message, this limit is slightly reduced to 153 characters per part.
In contrast, Unicode encoding has a significantly lower limit: only 70 characters for a single message, or 67 characters per part in multipart messages. This is due to the increased data size required to send Unicode characters.
Special Characters that impact SMS costs
Certain characters can trigger the switch from GSM7 to Unicode, resulting in a lower character limit and thus higher SMS costs. Here are some examples of characters that can impact encoding:
- Accented letters such as ä, ö, ü, é or è.
- Special symbols like |, ^, {, }, €, [, ], and ~.
- Characters formatted by text editors, such as “smart quotes” like ‘ instead of ', or “ instead of ".
- Backtick (`) and other non-standard punctuation marks.
When these characters are used, the SMS message is automatically sent as Unicode, reducing the available character count from 160 to 70 and potentially increasing the overall cost. To avoid this, it’s best to use simpler characters or the GSM7 default character set where possible.
Impact on SMS Costs
The difference in encoding formats is what causes some SMS messages to be charged differently. In your serial message, e.g. dunning run, if some SMS messages include special characters, they may be sent using Unicode, resulting in a higher cost due to the lower character limit.
For example, if your message exceeds the character limit for Unicode (70 characters), it will be split into multiple parts, leading to higher charges. This is why you might see a difference in cost, sometimes two or more times the cost of a single message from your text message service package.
By understanding the impact of character encoding, you can better manage your SMS costs and avoid unnecessary expenses.