Avoid Special Characters

SMS messages don’t support most special characters. For example, avoid using apostrophes as they can cause delivery issues or be replaced with unexpected characters on recipients’ devices. For more on special characters, see this guide.

Use Placeholders to Personalise Messages

You can personalise your SMS messages by including placeholders that insert contact-specific details when the message is sent.


There are two main types:

  • Text Placeholders (Personalisations) - Insert contact data, e.g., [FirstName]

  • URL Placeholders - Insert trackable URLs, e.g., [url=http://example.com]

The system automatically replaces these placeholders with the relevant data or a shortened tracked link like http://sm5.co/XXXXX.


WARNING: When you add links within the [URL=] component, it will automatically be shortened. Using a link shortener within this tool may cause the URL to not work as expected.

Opt-Out Links and Compliance

To help contacts easily unsubscribe, you can add opt-out links in two ways:

  • Automatically included opt-out link (default)

  • Manually added opt-out placeholder: Use [OptOut] or <OptOut> in your message text.

For example:
"Stop [OptOut]" becomes "Stop http://sm5.co/XXXXX"

You can also add opt-out links quickly with the ‘Add Opt Out Link’ button in the SMS editor toolbar.


 

Renting a Dedicated Opt-Out Word

For advanced SMS compliance, you can rent a unique opt-out word (e.g., "STOPNOW"). This enables recipients to reply with this word to unsubscribe.

  • Cost: £99 per month for a minimum of three months.

  • The word is unique to your account and must be rented through your Customer Success Manager.

  • If you stop renting the word, you risk losing ownership and may need to rent a new one.

Previewing Your Message

The SMS editor preview shows an estimated final message length and replaces placeholders with sample data. Keep in mind that actual contact data can vary in length, which may change the final message size and cost.

Maximum message length for an SMS Message is 160 characters. Multiple messages will be sent for greater lengths (using more credits). If you want to know more about technical limits, character counts, and input warnings, see our SMS Technical Guidance article.