What are concatenated SMS messages?

Concatenated messages refer to a method ...

Concatenated messages refer to a method used to overcome the typical character limit of a single text message (usually 160 characters).

How does it work?

With concatenated SMS, the sending devic...

With concatenated SMS, the sending device partitions a lengthy message into smaller segments and then reassembles them at the receiving end. To the recipient, this appears as one seamless, extended text. This technique allows for longer messages to be sent without disruption to the user experience.

Each segmented message is billed as an individual SMS, but the entire content is unified at the recipient’s end to form a single concatenated SMS message.

On networks that don’t support this feature, each segment is instead delivered as a separate SMS text message.

Character limitations

To ensure the segmented messages are lin...

To ensure the segmented messages are linked together seamlessly, a 7-byte concatenation header is used at the beginning of each SMS. Since this header is part of the message, it reduces the available space, limiting each segment to 153 characters. 

As a result:

• Up to 160 characters, charged as 1 message.
• Up to 306 characters (153 characters x 2), charged as 2 messages.
• Up to 459 characters (153 characters x 3), charged as 3 messages.
• Additional segments continue this pattern, with each segment allowing 153 characters and being charged as an individual message.

These reductions account for the information needed to properly link and order the segments upon reception.

For characters outside the standard GSM-7 set, e.g. special characters, which changes the encoding to UCS-2 encoding  the count is reduced from 70 to 67 characters per segment when you send concatenated SMS messages.

How to send a concatenated SMS message

Sending a concatenated message is straig...

Sending a concatenated message is straightforward and similar to transmitting a standard SMS:

• Write your message as you usually would, even if it exceeds 160 characters.
• Send the message, and the mobile network takes care of the rest. It will automatically divide the text into segments for transmission and reassemble them on the receiving device.

With this simple process, concatenated messaging enables more extended communication through SMS.