How to integrate with Constant Contact

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You will learn

Learn how to integrate Constant Contact with Klaviyo in order to migrate your data; the integration is designed to help you move from Constant Contact to Klaviyo. We don't recommend using both platforms at once other than during the interim period as you make the switch. Integrating consists of two main parts: a series of setup steps in Constant Contact/Mashery, and enabling the integration within Klaviyo.

From Constant Contact, Klaviyo pulls in the following data:

  • When someone received, opened, or clicked an email
  • Profiles of recipients who have unsubscribed or bounced, added to the suppression list
  • Existing lists in Constant Contact (you can choose to create Klaviyo lists from your Constant Contact lists)

Before you begin

It is important to note the following:

  • Data syncs from Constant Contact to Klaviyo once every hour.
  • The Constant Contact sync pulls new contacts from Constant Contact into Klaviyo so you don’t have to import them manually. Once your integration is set up, if a contact is added to a Constant Contact list, that contact will be synced into Klaviyo. However, if a contact is deleted from Constant Contact, they will not be deleted in Klaviyo.

Create an API key for Constant Contact

You’ll need a Constant Contact API key to integrate your Constant Contact account with your Klaviyo account. Since Constant Contact outsources part of their API infrastructure to Mashery, you’ll need to generate your Constant Contact API key in Mashery.

Create a Mashery account

  1. Start by creating a Mashery account or logging in to your existing account if you already have one. If you're creating a new account, use your own name and email address.
  2. Once you’ve filled out the registration form, click Register. Mashery will then send you a confirmation email, which you will need to open and confirm you new account.

Register an application and obtain an API token

Next, you'll need to obtain an API token which you'll use to pass your data from Constant Contact to your Klaviyo account. You'll do this by registering a new application and requesting an API key and secret.

  1. First, register a new app with Constant Contact.
  2. Name your application. In the example below, the application has been called ConstantContact Integration. We recommend you do not reference Klaviyo in your application name.
    Constant Contact Application Registration page with fields application name, company name, website, and application description
  3. In the box titled Select which Web APIs this application will use, ensure that Issue a new key for Constant Contact API and Standard API Access are both selected.
    Two settings checked under Select which web APIs this application will use
  4. Agree to the terms of service and click Register Application.
    Terms of service with checked checkbox and Register Application button with gray background
  5. You will need your Constant Contact Key and Secret to integrate with your Klaviyo account. Make note of both and keep them secure, as you will need these values. These can be retrieved later by navigating back to My Keys in your new app settings and selecting the correct application.
    Constant Contact application registration page with API key information blurred out

Update your OAuth redirect URI

Next, you'll update your OAuth Redirect URI so your application can connect with your Klaviyo account.

  1. Navigate back to your app settings and locate the application you just registered in the steps above. Click Edit.
    Constant Contact My Applications page Constant Contact Integration API information highlighted in white
  2. Fill in these fields:
    • Name of your application: Klaviyo Integration
    • Website: enter your URL, including either http:// or https://
    • Please describe what your application will do
    • Redirect URI for OAuth calls: enter
      Redirect URI Changes take approximately 10 minutes to take effect. During that time, calls using this API key will receive a redirect URI error response.
    • Register Callback URL: usually your website address, but may vary depending on your setup.
      Constant Contact Edit your Application page with fields including Redirect URI for OAuth calls
  3. Click Save. Your application is now ready to connect with Klaviyo.

Enable the integration in Klaviyo

Next, you'll use the Key and Secret from the application you registered above to connect your Constant Contact account to your Klaviyo account.

  1. Log in to Klaviyo, then click on your account name in the lower left corner.
  2. Select Integrations, then select the All Integrations tab.
  3. Search for Constant Contact, then click Add Integration.
    All Integrations tab in Klaviyo with constant in searchbar and Constant Contact card in results
  4. Expand the Advanced Options. We suggest you enable both the Collect open and click data for Constant Contact campaigns and Create Klaviyo lists from Constant Contact lists options.
    Constant Contact integration settings page in Klaviyo with API Key, API Secret, Advanced Options, and Connect to Constant Contact with blue background
  5. Click Connect to Constant Contact. You'll be redirected to Constant Contact. If you are not already signed in, you'll be prompted to enter your username and password.
    Constant Contact login page, image of laptop and hands on left side
  6. Click Allow. You should see the name of the application you registered.
    Allow Access? popup with Allow with orange background and Deny with white background
  7. You’ll be redirected back to Klaviyo where you will see a confirmation message at the top of the page.
    Constant Contact integration settings page in Klaviyo with green Integration updated banner

Klaviyo will begin to sync your contacts and the past 90 days of your event data. After the initial sync, Constant Contact syncs with Klaviyo every hour.

Data synced to Klaviyo

Once you've connected Klaviyo with Constant Contact, data will start syncing within a minute or two. If you click the Analytics dropdown, then select Metrics, you should see several metrics for Constant Contact data (received email, opened email, and clicked email) each with a Constant Contact icon next to it.

Metrics tab in Klaviyo filtered by Constant Contact showing metrics Clicked Email, Opened Email, and Received Email

While you may see the Received Email (Constant Contact) metric in your account, as shown above, Klaviyo does not currently record any of these events.

Next steps

Once your integration is enabled, you should consult our guide to migrating from your previous email service provider to Klaviyo for more information on switching providers. 

Additionally, to ensure that you maintain good deliverability, you should only send your first few email campaigns to an engaged segment of your list(s) from Constant Contact. Since you'll have open and click data from Constant Contact, you'll be able to use this data to segment your lists.

If you email your subscribers more than once a week, you should send your first week of email campaigns to an engaged segment. For more information, head to our guide to your first send.


You've now integrated Constant Contact with Klaviyo in order to start using Klaviyo to send emails.

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