Building Shopify Checkout Extensions: Customize and Enhance the Checkout Experience

Introduction

The checkout page is one of the most critical points in the eCommerce customer journey. While Shopify’s native checkout is fast and highly optimized, many merchants—especially on Shopify Plus—need more control and customization. That’s where Shopify Checkout Extensions come in.

Shopify Checkout Extensions allow developers to safely and flexibly customize the checkout experience. Whether it’s adding custom fields, integrating third-party services, or enhancing user experience, this feature gives you the tools to do so in a secure, scalable way.

In this guide, you’ll learn how to build and deploy Shopify Checkout Extensions, including setup, supported extension points, sample code, and best practices.

1. What Are Shopify Checkout Extensions?

Shopify Checkout Extensions are modular components that allow you to extend the Shopify checkout interface in specific, predefined areas using Shopify’s UI Extension API.

Key Features:

• Secure and PCI-compliant
• Built with modern tools (React, Shopify CLI)
• Embedded into the Shopify admin interface
• Compatible with the new one-page checkout
• Available only to Shopify Plus stores

Checkout Extensions are part of Shopify’s broader checkout extensibility framework and are intended to replace the legacy checkout.liquid method, which is being deprecated.

2. Prerequisites for Development

To build a Checkout Extension, you’ll need:

• A Shopify Partner account
• A Shopify Plus development store
• Node.js and npm installed
• Shopify CLI v3 or newer
• Familiarity with React and JavaScript
• Ngrok (or similar tool) for local HTTPS tunneling

Install Shopify CLI:

bashCopyEditnpm install -g @shopify/cli @shopify/app

3. Scaffold a Checkout UI Extension

Using the Shopify CLI, you can create a new extension from your terminal:

bashCopyEditshopify extension create

When prompted:

• Choose “Checkout UI Extension”
• Associate it with an existing app or create a new one

This will generate a project folder under /extensions with example code and a working React setup.

4. Use Checkout Extension Points

Extension points define where in the checkout flow your custom component will appear.

Common extension points include:

• Checkout::DeliveryMethods::RenderAfter
• Checkout::ShippingMethods::RenderAfter
• Checkout::OrderSummary::RenderAfter
• Checkout::LineItem::RenderAfter
• Checkout::PaymentMethods::RenderAfter

These are entry points for rendering React components via Shopify’s UI extensions API.

5. Create a Custom Field Example

Here’s a simple example that adds a custom delivery note field using the @shopify/checkout-ui-extensions-react library.

jsxCopyEditimport {
  reactExtension,
  TextField,
  useExtensionApi,
} from '@shopify/checkout-ui-extensions-react';

export default reactExtension('Checkout::DeliveryMethods::RenderAfter', () => {
  const { checkout } = useExtensionApi();

  return (
    <TextField
      label="Add delivery instructions"
      multiline
      onChange={(value) => {
        console.log('User entered:', value);
      }}
    />
  );
});

This field appears under the delivery method and collects additional instructions from the customer.

6. Preview Your Extension with Shopify CLI

To view your changes in a development store:

bashCopyEditshopify extension serve

This command:

• Starts a development server
• Connects to your store via Ngrok
• Allows live preview in the Checkout Editor

To preview, go to your development store > Settings > Checkout > Customize and add the extension block in the visual editor.

7. Deploy and Publish the Extension

Once you’re ready to move beyond development:

Push to Shopify:

bashCopyEditshopify extension push

Then, go to the Checkout Editor, drag your extension into the layout, and publish the changes.

Your extension will now be live and visible to customers during checkout.

8. Best Practices for Shopify Checkout Extensions

• Keep the UI simple and relevant to the checkout flow
• Avoid adding too many fields or distractions
• Validate all user inputs
• Use conditional logic to show extensions only when needed
• Follow Shopify’s accessibility and design guidelines
• Monitor and test after Shopify platform updates

9. Use Cases for Checkout Extensions

Checkout Extensions can enhance user experience and business operations:

• Collect delivery instructions or PO numbers
• Display loyalty points or reward summaries
• Show cross-sell or upsell offers based on cart contents
• Request additional verification or custom input for B2B orders
• Offer optional donations or rounding up for charity

10. Checkout Extensions vs. checkout.liquid

Conclusion

Shopify Checkout Extensions give developers a secure, high-performance way to customize the checkout experience. With structured extension points, a component-based architecture, and full support from the Shopify platform, they’re the future of checkout customization on Shopify Plus.

Whether you’re adding upsell logic, custom data fields, or real-time validation, Checkout Extensions make it easy to integrate with confidence.

At softwarehouse, we help Shopify Plus merchants unlock the full power of checkout customization with tailored solutions built to scale.

Need help building your custom checkout extension? Get in touch with our Shopify experts today.