Shopify will be sunsetting its Hosted Payment SDK and the legacy Sezzle payment gateway integration. If you are an existing merchant using our Sezzle payment gateway, please follow the migration steps to get started with the new Sezzle Payments app.

When configuring the app, use the API keys from your Dashboard account Sezzle US/CA Dashboard or Sezzle EU Dashboard.

This guide describes how to integrate Sezzle into your Shopify website so that you can provide Sezzle as a payment option for your customers. After integrating Sezzle, your Shopify site will:

  1. Offer Sezzle as a payment option on the checkout page.
  2. Refund Sezzle payments from your Shopify order management system.
  3. Display Sezzle promotional messaging.
  4. Authorize and capture payments.

Integration Steps Overview

  1. Install and configure the Sezzle Payments app
  2. Test your integration
  3. (Optional) Sandbox Testing

Before You Begin

  1. You should have a Sezzle merchant account.
  • Please visit our signup page if you don't have an account.
  1. Make sure you have the following Sezzle details handy.



  1. Familiarize yourself with the transaction flow when buying with Sezzle.

Install the Sezzle Payments app

  1. Click on Add app by navigating to the Sezzle Payments app.
  2. Once the app is installed, you will be prompted to enter your production Sezzle public and private API keys.
  3. Click update settings to verify your Sezzle account.
  4. You will be redirected to the payment settings page, where you will need to activate Sezzle Payments for your store.
  5. Click Activate.
  6. Once that is complete you should see Sezzle available as a payment method for your store.

To validate that you’ve successfully installed the new Payments App:
You should see Sezzle Payments installed in your Settings > Payments.

Please Note: After the Sezzle Payments app is installed, you will be prompted to enter your Public and Private API Keys. Please make sure you do this in order to successfully start taking transactions on the new Sezzle Payments app.

Install the Sezzle Widget app

  1. Log in to your website's Shopify admin.
  2. In your Sezzle Merchant Dashboard Setup Checklist (US/CA) or Sezzle Merchant Dashboard Setup Checklist (EU), click Install Sezzle Widget app.
  3. Click Get the App.
  4. Click Install App.

Configure Widgets

  1. Within the Sezzle app, enter your Public API Key and click link sezzle account.
  1. Once your account is linked, click add widgets to add widgets to your shop. This process may take a minute.
  1. After widgets have been added, navigate to a product page to confirm that the Sezzle widget has been added.
  1. If you ever need to remove Sezzle widgets from your shop, click the remove widgets button within the Sezzle app.

Note: If the Sezzle app is unable to automatically add widgets to your shop, one of our team members will automatically be notified and will work to manually add widgets to your shop within 7 business days.

Shopify Live Checkout

  1. In the Sezzle configuration page of your Shopify admin, enter the API Keys from your Sezzle Merchant Dashboard (US/CA) or Sezzle Merchant Dashboard (EU) and uncheck the Enable Test Mode checkbox, then save the configuration.
  2. On your website, add an item to your cart, then proceed to Checkout and select Sezzle as the payment method.
  3. Click Place Order.
  1. If you are redirected to the Sezzle checkout page, your integration is complete. Congratulations!
  2. Warning Don't complete the payment. Your checkout is now live, so you will be charged if you complete.


If testing was unsuccessful, review the following:

  • Sezzle Shopify extension is the most updated version.
  • Go to Apps > Sezzle, then click About. If there is an option to upgrade, do so now.
  • Sezzle gateway is activated.
  • Go to Settings > Payment Providers and ensure "Sezzle is active" is listed under the Alternative Payment Methods section.
  • API Keys were entered correctly.
  • It is recommended to use the Copy icon in the Sezzle Merchant Dashboard (US/CA) or Sezzle Merchant Dashboard (EU) to avoid typos or extra spaces.
  • If you have multiple accounts with Sezzle, the merchant ID and API Keys are tied to only one URL.
  • Widget script is present on your website and reflects the Merchant ID from your Sezzle Merchant Dashboard (US/CA) or Sezzle Merchant Dashboard (EU).
  • Go to a product page on your website.
  • Right-click then select Inspect.
  • In the Elements tab, search for widget.sezzle.

Manual Theme Integration

If the Shopify app fails to maintain the widget script on the product pages, or to add the script manually for additional pages, complete the following steps:

  1. Go to Sales Channels > Online Store > Themes.
  2. Click Actions, then select Edit Code.
  3. In the Code Explorer, go to the Templates folder and select the product.liquid file.
  4. Copy+paste the script to the very bottom of the file, then click Save.
  5. Repeat the previous step in the cart.liquid file.

Note: If you have additional custom product templates, step 4 will need to be repeated for each file, or the script added to a global file, such as layout/theme.liquid.

The script to be inserted into your webpage is as follows:


<script src="{sezzle_merchant_uuid}"></script>
Update {sezzle_merchant_uuid} in the above script template with your site’s Merchant ID (removing the curly brackets), which can be found in the Sezzle Merchant Dashboard (US/CA) or Sezzle Merchant Dashboard (EU).


<script src=""></script>

For assistance with widget configuration, click Request Addition of Widgets in the widget step of your Sezzle Merchant Dashboard Setup Checklist (US/CA) or Sezzle Merchant Dashboard Setup Checklist (EU).

Uninstall the Sezzle Widget app

  1. Go to Apps.
  2. Find Sezzle and click Delete.

Deactivating legacy Sezzle payment gateway

  1. On the Settings > Payments page, you will see Sezzle listed as a payment method.
  2. Click Manage.
  3. At the bottom of the page click Deactivate Sezzle.


Be sure to deactivate the "Sezzle" payment method and not "Sezzle Payments"

For more information on deactivating Shopify payment methods please visit this link.

If you have any questions, please reach out to [email protected] for more information.

Shopify Sandbox Testing

With the new Sezzle Payments app, sandbox testing can be enabled in your Shopify admin by navigating to Settings > Payments > Sezzle Payments, click Manage, check Enable test mode and click Save. Also, be sure to click the Manage button in Sezzle Payments, enter your sandbox API keys, check Testing with Sandbox API Keys and click update settings.

With the legacy Sezzle payment gateway, Sezzle offers an alternate sandbox payment gateway that can be used to test your integration. If you would like to install this gateway for testing, please reach out to our Merchant Success team at [email protected].