Segments

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SMS segments

SMS messages are sent in 160 character (140 byte) chunks known as message segments. Each SMS message you send will be billed based on the number of segments it contains. If a message is longer than the maximum number of characters allowed in a single segment, it will be split into multiple segments and reassembled on the receiving device as a single message. The numSegments field will tell you how many segments were used.

When you send multi-segment SMS messages, we must attach a data header to each message that tells the destination how to reassemble it. This takes up 6 bytes, leaving 153 characters for standard GSM-7 encoded messages. If the message contains any UCS-2 symbols, each message segment can only fit 67 characters (see below).

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MMS segments

Every MMS message, regardless of size, will always be counted as one segment. The maximum length of the message body must be less than 1500 characters.

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Special characters

If you include special characters like emoji in your SMS message body, we must use Unicode (UCS2) encoding to send the message. This means all characters are encoded using 16 bits, instead of 8 bits. Because of this, each segment can only contain 67 characters instead of 153. So, you may notice that messages that contain emoji or other symbols are billed at a higher rate. The numSegments field will tell you how many segments were used.

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Auto encoding

Sendo has a feature that detects common Unicode symbols and replaces them with their GSM-7 equivalent. This means that if your message contains a UCS-2 symbol like ‘ or —, we will convert them to ' and - respectively. This will allow your message to be sent using the more efficient GSM-7 encoding, using fewer message segments and saving you money. This is enabled by default, but can be turned off by contacting us.

Some common characters that are converted include: