What is concatenated SMS

What are concatenated SMS messages?

If you’re reading this, you’re probably here because you’ve come across the term ‘concatenated’.

It is a ridiculously obscure word that is only ever used in relation to SMS or an Excel formula. 

Let’s get this done…

What is concatenated SMS?

Text showing concatenated SMS

Concatenated SMS allows you to send and receive text messages that are longer than 160 characters.

Concatenated text messages are individual text messages of 160 characters that are linked together so that they arrive on the recipients’ mobile phones as one long text message rather than a string of individual texts.

If a text message is longer than the standard 160 character limit, then more than one text credit will be used to send the message.

So that longer texts arrive on the phone as one message, rather than a string of individual messages, the SMS messages are ‘concatenated’ or linked back together.

If you’re sending concatenated texts, the first text is 160 characters in length. Subsequent texts have a character count of 153.

The missing 7 characters are used as code to tell the mobile phone to combine the messages and display them as one long text.

What is the maximum length of a concatenated SMS?

The total length of a text message varies across the range of SMS API providers. The minimum is 459 (3 text credits) characters and the maximum is 1600 (11 text credits)

Even 459 characters is more than enough for most SMS marketing or transactional texts.

How can you send a concatenated SMS?

With most SMS providers, you don’t need to do anything different that you would for sending a message shorter than 160 characters.

The SMS provider will recognise that the text is longer than 160 characters and submit the text to the mobile phone network as a long text.

The mobile network will then do the job of splitting the text for transmission and combining back again on the mobile phone.

Delivery reports for concatenated SMS

SMS delivery reports allow the sender to discover whether a message was delivered or not.

The mobile networks provide one SMS delivery report for all long messages. They do not supply separate delivery reports for the individual messages that make up the concatenated text.

Longer messages are either delivered or not delivered, so you’d never get a situation where part of a long message arrived but not the rest.

How does concatenated SMS work for different languages

For languages like French or German that use the Latin alphabet, the standard protocol for sending messages is the GSM network protocol. This allows for 160 characters per text message.

For other languages, like Mandarin and Arabic that don’t use the Latin alphabet, then the unicode format is used, which has a hugely reduced character limit of just 70.

So using the unicode format, any message over 70 characters long will be concatenated. This obviously means that many more unicode messages are needed to send to the same length text as a GSM one. Bummer.

Free tools to help with SMS concatenation

We’ve build a free SMS message length calculator which shows how many characters and how many text credits will be used in a concatenated text.

Simply copy and paste or type in your message.

Concatenated SMS message length calculator

To help you identify if any of your messages contain Unicode characters, we’ve also developed a unicode character detector. Unicode characters will mean that messages will have an maximum 70 character and your concatenated messages will cost more.

Unicode detector for concatenated text messages

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author avatar
Henry Cazalet Managing Director
Co-founder and Director of The SMS Works, a low cost and powerful SMS API for developers. About Henry