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About Concatenated SMS (Short Message Service)
A concatenated SMS (Short Message Service) refers to joining multiple messages to overcome the character limit of an SMS message (160 characters). With SMS concatenation, you can send longer messages, enabling you to have meaningful interactions with customers on their mobile phones.
How does Concatenated SMS Work?
You can send a maximum of 1000 characters which will be split into 7 messages. Each SMS in a multi-part message can have up to 153 characters, in addition to the user-data headers (UDHs). UDHs are essential because they contain information about how the multi-part message should be processed such that the user receives it as a single SMS. If the mobile network does not support SMS concatenation, the message is delivered as multiple SMS messages.
For Unicode SMS with UTF-16 encoding, each SMS can have 70 characters. Unicode messages above 70 characters will be split into multi-part, messages where each segment of the multi-part SMS can have up to 67 characters.
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Concatenated SMS Character Limits |
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| Number of SMS | GSM | UTF-16 |
| 1 standard SMS | Max. 160 characters | Max. 70 characters |
| 2 Concatenated SMS | Max. 306 characters | Max. 134 characters |
| 3 Concatenated SMS | Max. 459 characters | Max. 201 characters |
| 4 Concatenated SMS | Max. 612 characters | Max. 268 characters |
| 5 Concatenated SMS | Max. 765 characters | Max. 335 characters |
Kaleyra’s robust SMS API allows you to seamlessly send long messages through concatenation. Learn more about our messaging solution here.