Add a banner to checkout

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

1. Navigate to your app directory:

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   cd <directory>

2. Run the following command to create a new checkout UI extension:

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   shopify app generate extension --template checkout_ui --name my-checkout-ui-extension

3. Select a language for your extension. You can choose from TypeScript, JavaScript, TypeScript React, or JavaScript React.

   Tip

   TypeScript or JavaScript is suitable for smaller projects that require a more straightforward API. TypeScript React or JavaScript React is suitable when you want an easy model for mapping state updates to UI updates. With JavaScript or TypeScript, you need to map state updates yourself. This process is similar to writing an application targeting the DOM, versus using react-dom.

   You should now have a new extension directory in your app's directory. The extension directory includes the extension script at src/index.{file-extension}. The following is an example directory structure:

   Checkout UI extension file structure

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   └── my-app

   └── extensions

   └── my-checkout-ui-extension

   ├── src

   │ └── Checkout.jsx OR Checkout.js // The index page of the checkout UI extension

   ├── locales

   │ ├── en.default.json // The default locale for the checkout UI extension

   │ └── fr.json // The locale file for non-regional French translations

   ├── shopify.extension.toml // The config file for the checkout UI extension

   └── package.json

1. Start your development server to build and preview your app:

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   shopify app dev

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

2. Press p to open the developer console. In the developer console page, click on the preview link for your extension.

Anchor to Export the extension targets from your script fileExport the extension targets from your script file

In your Checkout.jsx file, set the entrypoints for the checkout extension, and then export them so they can be referenced in your configuration.

For each extension target that you want to use, create a reactExtension function that references your target, and export it using a named export.

Anchor to Reference the extension targets in your configuration fileReference the extension targets in your configuration file

You can define more than one target so that app users can add the extension to multiple locations in the checkout.

In your checkout UI extension's configuration file, for each of your targets, create an [[extensions.targeting]] section with the following information:

• module: The path to the file that contains the extension code.

• target: An identifier that specifies where you're injecting code into Shopify. This needs to match the target that you exported from your file/s.

shopify.extension.toml is the configuration file for your extension. It contains basic information and settings.

Anchor to Define the required properties for the settingsDefine the required properties for the settings

Define the settings that you want to expose to app users in shopify.extension.toml. For each setting, define the required properties: key, type, and name.

The key property defines a string that's used to access the setting values from your extension code.

The type property determines the type of information that the setting can store. Each setting types has built-in validation on the setting input.

The name property defines the name for the setting that's displayed to the app user in the checkout editor.

Anchor to Define the optional properties for the settingsDefine the optional properties for the settings

For each setting, define the optional properties: description and validations.

The description property is displayed to the app user in the checkout editor.

The validations property defines constraints on the setting input that Shopify validates.

Anchor to Access app user settingsAccess app user settings

Retrieve the settings values within your extension. Set default settings so the app can be previewed without being deployed.

In React, the useSettings hook re-renders your extension with the latest values.

When an extension is being installed in the checkout editor, the settings are empty until an app user sets a value. This object is updated in real time as the app user fills in the settings.

Anchor to Add the Banner componentAdd the Banner component

Using the Banner component, create the custom banner.

Anchor to Start your serverStart your server

Run the Shopify CLI dev command to build your app and preview it on your development store.

Make sure that you select a development store that has enabled the developer preview for Checkout and Customer Accounts Extensibility.

1. In a terminal, navigate to your app directory.

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

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   shopify app dev

3. Press p to open the developer console.

4. In the developer console page, click on the preview link for the custom banner extension.

   The checkout opens.

This section describes how to solve some potential errors when you run dev for an app that contains a checkout UI extension.

Anchor to Property token errorProperty token error

If you receive the error ShopifyCLI:AdminAPI requires the property token to be set, then you'll need to use the --checkout-cart-url flag to direct Shopify CLI to open a checkout session for you.

Anchor to Missing checkout linkMissing checkout link

If you don't receive the test checkout URL when you run dev, then verify the following:

• You have a development store populated with products.

• You're logged in to the correct Partners organization and development store. To verify, check your app info using the following command:

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  shopify app info

Otherwise, you can manually create a checkout with the following steps:

1. From your development store's storefront, add some products to your cart.

2. From the cart, click Checkout.

3. From directory of the app that contains your extension, run dev to preview your app:

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   shopify app dev

4. On the checkout page for your store, change the URL by appending the ?dev=https://{tunnel_url}/extensions query string and reload the page. The tunnel_url parameter allows your app to be accessed using a unique HTTPS URL.

   You should now see a rendered order note that corresponds to the code in your project template.

Anchor to Test the the banner settings in the checkout editorTest the the banner settings in the checkout editor

1. In the development store where your app is installed, open the checkout editor: in the Shopify admin for the development store, navigate to Settings > Checkout > Customize.

2. In the checkout editor, select Add an app block, and then select your extension.

3. In the App block settings section, update the banner title, description, and status.

4. To preview your changes, do the following:

   1. From your development store's storefront, add products to your cart.
   2. Click Check out.
   3. View the banner on the first page of the checkout. The banner reflects the settings that you set in the checkout editor.