Migrate your app

The Storefront Cart API enables you to assemble a buyer's purchase, providing all relevant details back to the buyer before transitioning into the checkout process. This means you can add, remove, or update items in the cart, apply discounts, and more, before you create the checkout. Modifying a cart instead of a checkout provides your application a more feature-rich and performant way of assembly.

In the Checkout API, to handle errors you requested checkoutUserErrors:

With the Storefront Cart API, you request userErrors to receive information about errors that are related to the entire API surface:

Updating the cart enables you to adjust the line items, discounts, attributes, notes, and more, before finalizing the cart and sending the buyer to checkout. The Storefront Cart API provides the following main methods for updating line items in the cart:

• cartLinesUpdate

• cartLinesAdd

• cartLinesRemove

The cartLinesUpdate mutation behaves similarly to checkoutLineItemsReplace in the Checkout API. It replaces the existing line items in the cart with the new line items provided in the lines argument. This is useful when you want to completely refresh the cart contents.

If you want to add new line items to the existing ones in the cart, you should use cartLinesAdd. This enables you to build up the cart contents incrementally, without discarding the current lines.

With the Checkout API, discount codes aren't stackable:

The Storefront Cart API supports stackable discount codes. The discountCodes field in the cartDiscountCodesUpdate mutation is an array, which enables you to apply multiple discount codes to the cart:

The Storefont Cart API provides a straightforward way to attach both anonymous and authenticated buyer information to the cart using the cartBuyerIdentityUpdate mutation. The following examples compare updating a shipping address using the Checkout API and the Storefront Cart API.

The Storefront Cart API enables you to update the buyer's identity, including their delivery address, using the cartBuyerIdentityUpdate mutation.

You can retrieve the access token using either the customerAccessTokenCreate or customerAccessTokenCreateWithMultipass mutations.

In the Checkout API, you complete the checkout by retrieving the checkout web URL from the Checkout object's webUrl field. In the Storefront Cart API, you can retrieve the checkoutUrl from the Cart object at any point in the flow to send the buyer to the Shopify web checkout.