Build a post-purchase product offer checkout extension

In this tutorial, you’ll learn how to do the following tasks:

• Generate a post-purchase extension with Shopify CLI.
• Run the extension locally and test it on a development store.
• Build the extension UI with the component library.
• Authenticate requests from the extension to your app server.
• Deploy your extension code to Shopify.
• Create a version of your extension and publish it.
• Request access to run the post-purchase checkout extension on a live store.

• You're familiar with post-purchase checkout extensions.
• You've created a Partner account and a development store.
• You can place test orders on your development store.
• You've created an app that uses the Remix template.

To create a post-purchase checkout extension, you can use Shopify CLI, which generates starter code for building your extension and automates common development tasks.

In your app directory, run the following command to create a new post-purchase checkout extension:

You should now have a new extension directory that includes the extension script at src/index.{file-extension}.

Run the following command to install the dependencies required for the app server inside the extension directory that you created:

Post-purchase checkout extensions in production are hosted and served by Shopify. During development and testing, you need to use a Shopify browser extension to render your local extensions in checkout.

As you're testing, the browser extension automatically updates the checkout URLs.

1. Navigate to your app directory.

2. Either start or restart your server to build and preview your app:

   
   When you run the dev command, Shopify CLI builds and serves your app. It also instructs you through multiple configuration steps. If you've already run dev for this app, then some of these steps are skipped.

   To learn about the processes that are executed when you run dev, refer to the Shopify CLI command reference.

3. Press p to open the developer console. In the developer console page, click View checkout_post_purchase preview instructions next to your post-purchase extension.

   

4. Install the Shopify Post-purchase Developer Tools for Chrome browser extension.

5. Copy the post-purchase extension URL from the developer console.

6. In the browser extension settings, enter the extension URL from the developer console:

   

7. Place a test order in your development store and go through the checkout steps. The post-purchase UI is shown after the payment step, but before the Order status page:

The UI components for post-purchase checkout extensions are managed by Shopify to ensure that the checkout is fast, optimized for mobile, and integrated with Shop Pay.

Post-purchase extensions have access to the Checkout::PostPurchase::ShouldRender and Checkout::PostPurchase::Render extension points.

The extension points API provides helper functions to allow you to calculate potential order totals, update the order, modify metafields, and more.

Update the extension/my-post-purchase-ui-extension/src/index file with the following code. Replace the APP_URL constant, at the top of the file, with your local tunnel URL:

The following sections explain how different parts of the example extension code work.

The Checkout::PostPurchase::ShouldRender handler pre-fetches product data from the server that's running locally. You pass the token in the Authorization header so that you can authenticate it with authenticate.public in the Remix app, and POST the reference ID to the server. By doing this, you can verify that the request came from Shopify, and that the request is signed with the same secret key as the app.

The data returned from the server is then stored in the extension's storage.

Shipping costs and taxes are calculated based on the shipping address. The order changes are passed to the calculateChangeset function provided by the API. The returned data is used to update the UI.

The acceptOffer handler posts a request to the server to sign the changes as a JWT token. The request includes inputData.token, which the server uses to verify Shopify's request. The following code calls applyChangeset with the JWT token returned from the server.

Your app requires two endpoints to support the extension. The first endpoint is used to fetch the product data for the upsell. The second endpoint is used to sign the changeset, so Shopify can verify the request to edit the order that came from your app.

Create a new file called app/offer.server.js, which defines a function that's used to fetch the product data for the upsell. For simplicity in this tutorial, you'll hardcode the product data. The following logic can be replaced with an API call to Shopify or your own database:

You can use the following GraphQL query to fetch the first product in your Shopify store. Update the getOffer function with the data returned from the query, or the information from the product page in your Shopify admin.

In the app/routes folder, define two new routes. The first route is used to fetch the product data that you previously defined for the upsell. The second route is used to sign the changeset, so Shopify can verify that the request came from your app.

Both routes will verify that the request came from Shopify by checking that the JWT token is signed by the app's secret key using authenticate.public.

Add the following files to your project:

You are now ready to test your upsell functionality extension. Refer to Step 2 for testing in these instructions.

When you're ready to release your changes to users, you can create and release an app version. An app version is a snapshot of your app configuration and all extensions.

1. Navigate to your app directory.

2. Run the following command.

   Optionally, you can provide a name or message for the version using the --version and --message flags.

Releasing an app version replaces the current active version that's served to stores that have your app installed. It might take several minutes for app users to be upgraded to the new version.

If you want to run the post-purchase checkout extension on a live store, then you need to request access. Before you request access, you need an unpublished app in a development store.

After your access request has been approved, any apps that you distribute through the Shopify App Store also need to be submitted for review in the Partner Dashboard. The review process is slightly different for existing apps and new apps.

For existing apps:

• You need to test your app using an unpublished app in a development store.
• To add the post-purchase checkout extension to a published app, you must submit the unpublished testing app for review in the Partner Dashboard.
• If the new app meets the stated requirements, then it will be approved and the post-purchase extension can be added to your existing published app.

For new apps:

• You need to test your app using an unpublished app in a development store.
• To add the post-purchase checkout extension to a published app, you must submit the unpublished testing app for review in the Partner Dashboard.
• If the new app meets the stated requirements, then it will be approved and listed in the Shopify App Store.

1. From your Partner Dashboard, click Apps.
2. Click the name of the app that you want to change.
3. Click API access.
4. On the Access post-purchase extensions card, click Request access.
5. In the Post-purchase page that opens, describe why you're applying for access.
6. You'll see a banner that your request is under review. The review process can take up to seven days.

After your request is approved, you're notified in the Partner Dashboard that your app has full access to the post-purchase extensions.

• Learn how to create a post-purchase subscription upsell.
• Review the post-purchase targets API reference.