This guide describes how to get started with bundles, and describes the available implementation options.

## How it works

To create a bundles app, you need to configure a bundle and create a bundle UI extension.

### Bundles configuration

To configure a bundle, you can do one or both of the following tasks:

  * Implement the bundles product API to implement a fixed bundle.
  * Create a bundles Shopify Function to group lines together as they’re added to the cart, with configuration data in metafields. When you create a bundles Shopify Function, you need to build a theme app block. This block replaces the variant picker in Online store themes to add all of the required bundle components.

### Bundle UI extension

  * Create a bundle UI extension to summarize bundle components for Shopify admin product and product variant pages.
  * Configure app extension for bundles app link to create and update bundle components, from the Partner Dashboard.
  * Create pages in your embedded app using Shopify App Bridge to allow users to perform the following tasks:
      * Configure bundle components for creating a new bundle product.
      * Update an existing bundle.

## Implementation

Apps can configure and operate bundle products in the following ways:

- **Fixed bundles**: Lets users configure product variants that are fulfilled with a bundle of products as a product grouping API.

- **Customized bundles**: Uses the [`cartTransform`](/docs/api/admin-graphql/unstable/objects/CartTransform) object to convert a group of products added to the cart into a bundle and adjust the price automatically.

    > Note:
    > In this documentation, we'll exclusively cover the customized bundles with functions implementation path.

The following table provides a comparison of the two implementation options:

| | Fixed bundles with the [`productBundleCreate` mutation](/docs/api/admin-graphql/unstable/mutations/productBundleCreate) | Customized bundles with [`cartTransform` object](/docs/api/admin-graphql/unstable/objects/CartTransform) |
| - | - | - |
| **Admin Configuration** | - | - |
| **Definition** | Using the GraphQL Admin API | Through the [`cartTransform`](/docs/api/admin-graphql/unstable/objects/CartTransform) object, and the metafields and metabjects on that object. |
| **Pricing** | The price is derived from the parent variant.<br/><br/>The bundle price is allocated across components in the checkout, cart, and orders using a weighted price algorithm. | For expand, the price is derived from the parent. For merge, the price is derived from components, with a price adjustment applied in the function. <br/><br/>The bundle price is allocated across components in the checkout, cart, and orders using a weighted price algorithm. |
| **Discounts** | Discount calculated on the parent then allocated on the components. | Discount calculated on the parent then allocated on the components. |
| **Taxes** | Taxes will be computed on the components. | Taxes will be computed on the components. |
| **Storefront** | - | - |
| **Product details page, buyer chooses** | Parent bundle variant<br/><br/>Works without Liquid change<br/><br/>Sellable quantity is available through Liquid | Multiple component variants<br/><br/>App is responsible for its own variant picker on the product details page<br/><br/>Sellable quantity is only available through the Storefront API |
| **Cart add** | **Input**:<br/>Parent bundle variant<br/><br/>Displayed as grouped in cart and checkout<br/><br/>**Output fields**:<br/>In cart, potential to query `cart.line.components` | **Input**:<br/>Multiple component variants<br/><br/>Displayed as grouped in cart and checkout<br/><br/>**Output fields**:<br/>In cart, potential to query `cart.line.components` |
| **Oversell protection** | **Always**: Shopify maintains sellable quantities on the parent bundle variant.<br/><br/>The parent inventory quantity is the minimum of the component's inventory quantities. | **Storefront**: App maintains instock/out of stock for the parent.<br/><br/>**Post-add-to-cart**: Components are always checked in cart and checkout providing some built-in oversell protection. |
| **Bundle grouping** | Grouped by bundle parent variant ID (item added to the cart) | Grouped by bundle parent variant ID (assigned by function) |
| **Admin Orders** | - | - |
| **Default fulfillment constraint** | No fulfillment constraint | No fulfillment constraint |
| **Store in order lines** | Components, with reference to parent through groupings | Components, with reference to parent through groupings |
| **Refund/Returns** | Operates at the component level | Operates at the component level |
| **Reports** | Sales reporting at the component level | Sales reporting at the component level |

## Next steps

- [Add a customized bundle](/docs/apps/build/product-merchandising/bundles/add-customized-bundle) using Shopify Functions.
- [Add a fixed bundle](/docs/apps/build/product-merchandising/bundles/add-fixed-bundle) using the GraphQL Admin API.