Configure BigCommerce Embedded Checkout with a custom storefront and pass customer login state securely using customer impersonation tokens

Steps

1. Generate a customer impersonation token via the GraphQL Admin API using POST /graphql with the customerImpersonationToken mutation, providing the customerId and channelId; this returns a short-lived token
2. Create a cart on behalf of the logged-in customer using the Storefront GraphQL API with the generated impersonation token in the Authorization: Bearer header; include customerId in the createCart mutation input
3. Fetch the checkoutUrl from the cart via the Storefront GraphQL API cartQuery; the URL will include the customer session context
4. Render Embedded Checkout by calling embedCheckout({ containerId: 'checkout', url: checkoutUrl }) with the SDK; the iFrame will display the checkout pre-populated with the customer's saved addresses and payment methods
5. Pass the channelId to all Storefront API requests to scope cart and checkout to the correct storefront channel in a multi-storefront setup
6. Test customer-specific checkout behavior (saved cards, loyalty points) by using a test customer account with known credentials in your staging environment