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Does Twilio support concatenated SMS messages or messages over 160 characters?

Yes. With the Messages resource URI, you can send and receive messages containing up to 1,600 characters. These long SMS are called concatenated messages.

Please note, while sending SMS messages up to 1,600 characters is possible, Twilio recommends keeping your SMS shorter for the best user experience, lower cost, and optimal deliverability – keeping messages to 320 characters or fewer is a good guideline. For more info about message length, see Maximum Message Length with Twilio Programmable Messaging.

Sending outbound concatenated SMS

Concatenated messages are supported when sending to all major US/Canada carriers except for US Cellular, who do not support concatenated SMS. Many carriers worldwide as well as many smaller US/Canada carriers also support concatenated messages.

When sending concatenated SMS, Twilio will auto-segment long messages with a special header, which mobile carriers can use to reassemble the segments on the destination handset. Thus, concatenated SMS can appear as one single message on the receiving device. Note that special header needs to be appended to handle concatenated messages, so each segment can only contain up to 153 characters. Messages with one or more non-GSM characters have to be sent using UCS-2 encoding and can only contain 67 characters per segment for multi-part messages.

Refer to our FAQ for how pricing works for outbound concatenated messages.

Please note, when sending very long SMS messages (longer than 10 segments with Unicode characters) some mobile carriers may have trouble handling these messages. It is advisable to keep your messages shorter than 10 segments if possible.

For extensive details on how GSM vs. Unicode encoding works, and how this relates to concatenated messages, see: What the Heck is a Segment?

What happens when sending to a carrier that does not support concatenated messages?

Even if a mobile carrier does not support concatenated messages, you can still send long SMS to recipients on that carrier. Twilio will divide your long message into individual SMS to meet the character limit, and automatically add page information to the beginning of each one, for example (1/2), (2/2). On Twilio, your message will still appear under a single Message SID.

A note about US Cellular: 150-character limit

In addition to not supporting concatenated messages, US Cellular also limits the length of a single message to 150 characters in GSM encoding, instead of 160. This means that long messages to US Cellular may segment differently than those sent to other networks.

A single Unicode-encoded message to US Cellular can be up to 70 characters long, the same limit as other mobile carriers. 

Since US Cellular does not support concatenated messages, multi segment messages will include the segment number ("1/3", "2/3" etc.) and be limited to 142 characters for GSM-encoded messages and 64 characters for Unicode-encoded messages. 

Receiving inbound concatenated SMS

Similarly, Twilio supports inbound concatenated messages up to 1,600 characters. Inbound messages over 160 characters long will be received on your Twilio phone number as one single message, as long as the sending carrier supports concatenation. The price of the inbound message will be the sum of the total number of segments.

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