The input settings of your computer will have an effect on the character encoding, and as a result the number of characters you can include in a single text message. We currently support GSM encoding 03.38 (standard and extended). Anything else will automatically be converted to UTF-16 encoding.

The different encoding types result in the different character limits because of the size of the individual characters in the message: Latin1 characters are 1-byte characters, whereas UTF-16 are 2-byte characters.

To help compensate for the limited characters per SMS, some mobile phones and networks support SMS Concatenation. This is where extra-long SMS message content is split into multiple messages when it is sent, and is then recombined into a single message by the recipient device. To the recipient it looks like one long SMS, and the concatenation is nearly transparent, with the exception that each message is billed separately.

If an SMS is sent with 240 characters (GSM encoding) then it will be processed as two separate messages, and billed accordingly.

GSM encoding:

• One standard SMS message = 160 characters (max)
• Two concatenated SMS messages = 306 characters (max)

UTF-16 encoding:

• One standard SMS message = 70 characters (max)
• Two concatenated SMS messages = 134 characters (max)

As with email, SMS content should not:

• Violate any laws or regulations.
• Be deliberately deceptive.
• Contain obscene or pornographic content.
• Be harmful to minors.
• Be defamatory in nature.
• In some regions, special regulations apply to commercial content for gambling.
• In certain cases, pre-registration of the sender ID (From) is needed.
• To some destinations, the whole content template needs to be pre-approved by the authorities.

Some additional tips:

• Content should always include a clear and relevant call-to-action stating the purpose of the message, for example a reminder, discount, sale, etc.
• Personalize any external links and use these in combination with attractive offers to not only improve campaign performance, but to help reduce opt-out requests.
• For example in the US, affiliate marketing is not allowed, third-party associates must be named, and the sender must be always identified in the message. Nevertheless, regulations differ by countries or regions. So as a generic rule, always learn about your local regulations regarding the content of SMS marketing messages.

Sending marketing SMS content requires a separate, visible and explicit opt-in, which means that if a contact has opted-in for email content you must not send them any SMS content just because you also have their mobile number. You can (and should) use double opt-in for SMS in the same way as you do for email, with the contact signing up on your website followed up by an SMS opt-in confirmation request being sent to them for agreement.

A best practice double opt-in message is made up of the following:

• Clear description of what content they will receive.
• An indication of how often they will receive messages.
• Clear description of how the customer can opt-out of the service at any time.
• Any associated data rates and/or costs that may apply.*
• A list or a link to the Terms and Conditions.
• A list or a link to the Privacy Policy.

A best practice SMS opt-in confirmation message is made up of the following:

• Identification of the sender.
• Message frequency.
• How to opt out.
• Any associated data rates and/or costs that may apply.*

*This is mandatory in many countries or regions, check your local regulation if it applies to you as well. The following phrase must be included exactly as is: "Msg&Data rates may apply".