Guide to crafting SMS and MMS messages

You only have a matter of seconds to make an impression on your recipients. When you keep your message short, your recipients can see the value of a text immediately.

Further, SMS messages are limited to:

• 160 text characters normally
• 70 characters if there are any symbols, emojis, or special characters
  • Symbol examples: © and ™
  • Special character examples: λ and ń

If you have any personalization or event variables, your messages won't all have the same number of characters in them. For instance, let's say you want to include someone's first name using the variable {{ first_name|default:'friend' }}, and Klaviyo estimates 6 characters for a first name. However, if your recipient's name is "Alexander," the actual character count is 9. Thus, it's important to leave a few extra characters in your SMS.

Note that when an SMS extends beyond 1 message, Klaviyo includes a header on the backend so that carriers know the 2 sends go together. The header takes around 7 characters for every message segment, meaning that 2 SMS segments have a total character limit of 306. 

As a best practice, always include a link in your SMS messages and use Klaviyo's link shortener.

A key metric for SMS is click rate, as almost all SMS messages are opened. If there's no link in the message or the link is not shortened, you won't have insight into how your SMS and MMS messages are performing, as Klaviyo won't be able to track the messages. Shortened links are typically 24–25 characters, but this can vary.

If you want iOS 10+ users to see a preview of your link, you need to do two things:

• Include http:// or https:// at the start of the link
• Place the link at the very beginning or end of the message

Note that for this to work, the link cannot be followed by any other text (including opt-out language). Further, this only works when there is only one link per message.

Just like with email, SMS messages tend to perform better the more they are personalized to the recipient. However, note that when using variables, the exact character count will vary depending on the recipient.

To add personalization via profile properties, you can use any of the properties in the Personalization dropdown, which shows all of the custom and profile variables available in Klaviyo. Using this, you can, for example, address the recipient by their first name, if it's known. If it's not, you can use a generic term, such as "friend."

In flows, you also have the option of adding event tags. For instance, in an abandoned cart flow, you can show the name of the first item someone left behind.

SMS is more heavily regulated than most other marketing channels, so it's especially important to be mindful of compliance. Failure to adhere to these laws may result in anything from carriers blocking your messages to fines.

Depending on your recipient's location, different rules may apply. To make it easier, we recommend not adjusting the settings in the Compliance tab. These option will apply only to recipients in the countries listed below the option, and are considered to be the best practice for those areas.

Note that either unsubscribe instructions or an opt-out link is typically required.

You need to have the proper permission to text someone. In most countries, it's illegal to send an SMS or MMS to anyone who hasn't explicitly opted into SMS marketing. Just having someone's phone number is not enough. 

Make sure you’ve obtained a customer’s phone number from a legal source (i.e., signup form, in-person event, opt-in on a checkout page). Klaviyo will never send an SMS to a profile that doesn’t have consent. For more information head to the article on how to collect SMS consent.

It’s best practice to text a single SMS recipient anywhere from 2 to 6 times a month. Like your emails, you’ll want to make sure that you stick to a regular schedule when sending out your SMS messages.

Additionally, create a customer journey for someone who signs up for your welcome series or abandons a cart, and figure out how often you’re communicating with that person. You don’t want to communicate too little or too much with a customer. Anywhere between 2 and 6 messages a month is a good cadence to start.

While it may be tempting to use text-speak or acronyms to make your messages shorter, it's not recommended.

Unless you know your audience both understands and prefers them, using acronyms may confuse your recipients.

If your audience will know and appreciate text-speak, still be careful of overusing it (i.e., don't use it for the majority of the message).

While each audience is different, typically MMS performs similarly to SMS. In terms of performance, SMS tends to perform better than MMS in most cases.   

MMS is also not available in every country. When it is available (e.g., US and Canada), MMS messages more credits than SMS.

That being said,GIFs and static and dynamic images can enhance your text messages. They can be good for product launches or abandoned cart reminders. We recommend testing how MMS perform for you to see where MMS makes the biggest impact.

Emojis can make an impact, but like acronyms and text-speak, should be used sparingly. Overusing them may annoy your audience, and not every audience responds to emojis positively. Emojis can take the place of words, but having an entire message be emojis may confuse recipients. 

We recommend testing emojis on your audience to see if they prefer them and find out how often you should send them. 

Keep in mind that using just 1 emoji reduces the character count for an SMS from 160 to 70.

As you send out your texts, you’ll want to send them between 9 a.m. and 8 p.m. in the recipient's local time. Most likely, sending an SMS too early in the morning or too late at night will lead to fewer conversions and more people unsubscribing from communication with you.

For flows, there are quiet hours, which restrict the times when SMS messages can go out based on the country code for the recipient's phone number. For campaigns, you must segment your subscribers by country and be conscious of their local time. Klaviyo warns you if your campaign will potentially violate quiet hours.

Test when your recipients like to hear from you. For instance, many ecommerce businesses find that sending around noon on Sunday leads to better performance.