Understand SMS Sending Numbers

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Please note that only account Owners and Admins will have the ability to add/manage sending numbers.

The number you send from has a large impact on your SMS marketing. It can affect your deliverability, what you can send, and who you can send to. 

In this article, we go over the different number types, including what they allow you to do, how fast they send messages, and where you can use them.

Getting Your Sending Number

There are two main ways of getting a sending number:

  1. Using the number(s) built into your plan
  2. Porting the number from another SMS provider

All SMS plans include an alphanumeric sender ID and either a toll-free number or, pending approval, a short code. 

Porting a Sending Number

If you already use SMS and want to keep the same sending number, you can port it into Klaviyo. Note that porting a number will result in the loss of any voice capabilities. There is no extra cost to port numbers. 

We can port over toll-free numbers and short codes; however, this does not apply to shared short codes. If you previously sent from a shared short code, you will instead need to request a brand new number

Further, it's not possible to port alphanumeric sender IDs; however, you can set the sender ID to be the same as your previous ID. 

  1. Navigate to Account > Settings
  2. Click SMS
  3. Click into the Request Additional Numbers dropdown
  4. Select Port an Existing Number 
  5. Click Submit Port Request

After you submit your port request, you can expect to be contacted by a Klaviyo representative. 




Sending Number Types in Klaviyo

As of October 1, 2021, Klaviyo no longer supports long numbers. We recommend using a toll-free number instead. 

There are several types of numbers used for sending SMS in Klaviyo: 

  • Toll-free numbers (US and Canada)
  • Short codes and vanity short codes (US or Canada)
  • Alphanumeric sender ID (UK only)

Below, we've outlined the major differences between the different number types.

Number Type

Price per Month

Time to Provision

Toll-free number

Free with your SMS plan


7–10 days for verification


Free with your SMS plan


Short code

$650 per month

8–12 weeks

Vanity short code

$1,150 per month 

8–12 weeks

Sending Speeds

Alphanumeric sending IDs have a sending speed of 10 msg/second.

All other number types send as quickly as possible. That said, MMS sent via toll-free numbers will send slower. The primary reason for this is because MMS messages contain a lot more data than SMS, and thus take more resources in order to be successfully delivered. 

Toll-Free Numbers (US and Canada) — +1 8XX-XXX-XXXX

Toll-free numbers are available as soon as you select a plan or request a toll-free number. Toll-free numbers can also be verified, although this is not available for all industries. 

As of May 15, 2022, all toll-free numbers must be verified in order to send SMS. Wireless carriers will no longer deliver messages from unverified toll-free numbers. For more information, please read Understand toll-free verification

You can only have one toll-free number per account.

Short Codes/Vanity Short Codes (US and Canada) — XXX-XXX

Short codes and vanity short codes are essentially the same type of number. The only differences are that with vanity short codes, you can pick your number.

Not all businesses and industries are eligible for a short code. You must apply for them and be approved. This approval process takes several weeks, so even if you are eligible, you cannot instantly start sending on a short code. 

Further, short codes are only good for the country they were approved in. If you have a US short code, you cannot use this short code for Canadian recipients, and vice versa. 

MMS is also not available for Canadian short codes. 

Alphanumeric Sender IDs (UK and AUS)

Alphanumeric sender IDs are the only SMS sending numbers available in the UK and Australia. They are made up of a mix of numbers and letters. 

Unlike the other sending number types, alphanumeric numbers have a sender ID that you can customize. Rather than recipients getting a text from a number, they’ll see it come from, for example, your brand name. In Klaviyo, you can customize the sender ID, although it must be between 3-11 characters, have at least 1 letter, and contain no special characters. These numbers don’t have to be unique either, so you can make the ID be whatever fits your brand 

You can also change the ID at any time, and it will not affect your deliverability. 

In general, alphanumeric messages cannot receive text messages or send MMS, meaning the following is not available: 

  • Subscribe/unsubscribe keywords
  • SMS conversations 
  • MMS

When someone texts your alphanumeric sender ID, they will see that the message was not delivered. 

Since recipients cannot opt out using keywords (e.g., “STOP”), they must unsubscribe via a link. When creating a message in Klaviyo, you can add this link automatically via the X option in the Compliance tab.


Since subscribers also can't confirm that they want to sign up, single opt-in is automatically enabled for any UK or Australian SMS subscriber — even if the list they join is set to double opt-in

How to Add a Number

If you want to add a number not included in your plan, you can request an additional number. Keep in mind that any numbers not in your plan cost extra. 

To add a number, navigate to Account > Settings > SMS.

Under Sending Numbers, click Additional Numbers. 


Select Request Additional Numbers.

Then, choose one of the following options:

  • Toll-free number (1-8XX-XXX-XXX)
    You can only have one toll-free number per account. If you already a toll-free number, you will not be allowed to add another.
  • Short code (XXX-XX)
    When you select this option, you will initiate the process of leasing a short code. We do not currently support shared short codes, meaning your short code will be unique to your business. When you request a short code, you will see your request move to a pending state and will receive an email from a Klaviyo representative regarding next steps.
  • Vanity short code (XXX-XX)
    When you select this option, you will see your request move to a pending state and will receive an email from a Klaviyo representative regarding next steps. You will then work with this representative to specify which numbers you would like included in your short code, provided the number is available.

You can also only have one alphanumeric sender ID per account. Since these numbers are included in every plan, there is no option to add them. 

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