Migrate from Postscript to Klaviyo

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When migrating from Postscript, you can upload your existing list of SMS subscribers to Klaviyo to start building out your SMS marketing strategy right away. Importing your SMS contacts allows you to centralize customer data so you can leverage Klaviyo’s robust analytics and tailor your customers' experience through the use of SMS-integrated flows, emails, and push notifications.

This guide will walk you through migrating your data from Postscript to Klaviyo using a simple bulk export.

Designate an SMS Sending Number

When you enable SMS in Klaviyo, you'll be prompted to choose an SMS plan.

All SMS plans include a free sending number. For lower-cost plans, this is a toll-free number, while for higher plans, it is a short code. Note that you must be approved for a short code, and not all businesses are eligible. Further, the short code approval process can take several weeks, so please allow time for the creation of a new short code when planning your SMS migration.

If you indicate that you already have an SMS number, our Support Team will contact you regarding porting your number over to Klaviyo. Klaviyo does not currently support porting long numbers.

If you do not already have a short code that you would like to port over, it can take several weeks to be assigned a new short code. Please allow time for the creation of a new short code when planning your SMS migration.

Klaviyo does not require that you send a final text out of your current SMS provider as part of the migration process. This is not required for the port to be successful; however, it is considered a best practice. Read this article on how to inform your customers about a change in phone numbers

Export SMS Subscribers from Postscript

Before you begin migrating your SMS contacts from Postscript into Klaviyo, it's important to distinguish between subscribers who have opted-in to SMS messaging and those who have not. It is against Klaviyo's Terms of Service and TCPA laws to market to contacts who have not explicitly opted-in to receive SMS communication from your business.

Klaviyo identifies opt-in subscribers as those who have a phone number and an SMS Consent Timestamp associated with their profile. In Postscript, this timestamp may be assigned to the field subscriber_created_at_utc in your export file. Klaviyo will only send SMS messages to contacts who have both a phone number and an SMS Consent Timestamp stored within their Klaviyo profile.

Postscript allows you to export a list of all SMS subscribers directly from your account into a CSV file. This list will simplify the import process into Klaviyo.

To begin, log in to your Postscript account or navigate to it from your ecommerce store’s connected apps. From the Postscript dashboard, click your account name dropdown in the upper right corner and select Account.


On the Account page, scroll down to the Exports section. Select Subscriber Export from the dropdown menu and then click Export. Postscript will process your export request and alert you when the subscriber list is complete and ready for download. Keep in mind that the larger your list of SMS subscribers, the longer the export will take to generate.


When your subscriber list is ready, click Go To Reports to be redirected to the Reports page where your list is available for download.


Your newly exported list will appear under Report Name as Active Subscribers Export along with a download link and timestamp. If you have more than one subscriber export, use the timestamp provided to identify the most recent export. Click Download to retrieve the exported CSV file from Postscript.

Format Subscriber List CSV

You should carefully format your CSV file before importing it into Klaviyo. This will ensure that your contacts are imported smoothly and accurately. Postscript’s exported CSV file includes all the columns you will need, along with some additional columns you may choose whether or not to import. 

You will likely want to include these columns in your import:

  • first_name
  • last_name
  • email

If the following columns appear, you may wish to either remove them from your import, or map them to new fields in your Klaviyo account. Consider whether or not these fields are valuable to you, and remove the columns if you choose. 

  • customer_id
  • last_keyword_subscribed_to
  • automation_and_campaign_texts_sent_count

The phone number column is required to import your SMS contacts. Check the format of the phone numbers in your CSV file. Phone numbers must be in one of the following formats:

  • E.164 (e.g., +12345678910)
  • RFC966 (e.g., +12-34-567-8910)
  • E.123 national (e.g., 12345678910) 
  • international formats (e.g., +12 345 678 910)

Klaviyo requires an SMS Consent Timestamp column, so you will need to rename the appropriate column heading. Locate the column heading subscriber_created_at_utc and delete the text, renaming it SMS Consent Timestamp. Doing so allows your import to automatically map the values to the correct field in Klaviyo.


Timestamps need to be specifically formatted or Klaviyo will not recognize them as timestamp fields. Postscript exports timestamp data in the format MM/DD/YYYY HH:MM:SS by default. However, the format MM/DD/YYYY HH:MM will also import correctly. For additional supported timestamp formats, check out the guide here.

Import Subscriber List to Klaviyo

After you've formatted your export data, you can import it into a Klaviyo list. To begin, log in to your Klaviyo account and navigate to Lists & Segments.

Click Create List / Segment in the upper right corner to create a new list for your SMS Subscribers. On the next page, select List.

Give your new list a name, such as Postscript SMS Subscribers and click Create List.


Once your new list is created, click Upload Contacts to add your SMS subscribers via import. Drag and drop your CSV file into the field provided, or select it from your computer to upload your contacts. After selecting your file, Klaviyo will process the import and display a green loading bar with the text Uploading and validating file… If any required columns are missing, Klaviyo will alert you with an error message.


If you would like to add the contacts to an existing list, locate the list where you'd like to upload your contacts. Then, click the menu to the right of the list and select Import Data. Drag and drop your CSV file into the field provided to upload your contacts. 


For more detailed instructions on adding new contacts to a list, head to our article on Creating and Adding Contacts to a List.

Whether you create a new list or update an existing list, you will be prompted to review field mapping before Klaviyo begins the import. Carefully review each import field/corresponding Klaviyo field, and modify them as needed. By default, all identified fields are included in the import. You can omit a field from the import by unchecking the box to the right of the field name.

Here is an example of field mapping for an SMS contacts import from Postscript:


Import fields that are not automatically matched to a Klaviyo field are marked as Unmapped. If you try to import an unmapped field, an error message will appear, prompting you to map the field. From the dropdown, select an existing Klaviyo field name or create a custom field by typing a name into the blank entry field. To the right of the field name, select a data type from these options: String, Boolean, Numeric, Date, or List. If you're unsure of the data type, head to our article on data types in Klaviyo.

When you are satisfied with the field mapping, click Import Review on the upper right-hand corner of your screen. Review your selections, taking special note of SMS Consent verification. When finished, click Start Import.


Your import will begin shortly. Depending on the length of your contact list, the import may take some time. You can stay on this page to watch the upload progress, but it is not necessary. Klaviyo will also send you an email confirmation as soon as the import is complete.

After the import finishes, you will see a summary of the completed import which includes a report of any skipped records. If your CSV file contains improperly formatted data, those fields may fail to import properly. When this occurs, you can download a report of the skipped records, resolve any formatting issues, and retry importing those records.


For a deeper dive into importing contacts, head to our article on Migrating Existing Subscribers and Unsubscribes into Klaviyo.

Create a New SMS Segment

When your SMS contacts are successfully imported to a Klaviyo list, create a new segment to begin tracking and analyzing your subscribers.

Navigate back to Lists & Segments. Click Create List / Segment in the upper right corner to create a new segment of your SMS Subscribers. On the next page, select Segment.


Give your new segment the definition: If someone is or is not consented to receive SMS and select is from the dropdown list. Then click Create Segment. To learn more about creating segments for SMS subscribers, check out our SMS Segments guide.

You are now ready to start integrating SMS into your campaigns and flows. Check out the additional resources below for guides on getting started with your SMS strategy.

Additional Resources

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