--- title: Start building bundles description: >- Learn how to get started with bundles and get familiar with the implementation options. source_url: html: >- https://shopify.dev/docs/apps/build/product-merchandising/bundles/start-building md: >- https://shopify.dev/docs/apps/build/product-merchandising/bundles/start-building.md --- # Start building bundles 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 You can use a Bundle UI extension to display and manage bundle components in the Shopify admin: * Create a [Bundle UI extension](https://shopify.dev/docs/apps/build/product-merchandising/bundles/product-configuration-extension/add-merchant-config-ui) that summarizes bundle components on product and product variant pages in the Shopify admin. * Create an [admin link extension](https://shopify.dev/docs/apps/build/admin/admin-links/create-admin-links) that opens your app to create or update bundle components. * Build pages in your app using [App Bridge](https://shopify.dev/docs/api/app-home) so merchants can: * Configure bundle components when 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`](https://shopify.dev/docs/api/admin-graphql/latest/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](https://shopify.dev/docs/api/admin-graphql/latest/mutations/productBundleCreate) | Customized bundles with [`cartTransform` object](https://shopify.dev/docs/api/admin-graphql/latest/objects/CartTransform) | | - | - | - | | **Admin Configuration** | - | - | | **Definition** | Using the GraphQL Admin API | Through the [`cartTransform`](https://shopify.dev/docs/api/admin-graphql/latest/objects/CartTransform) object, and the metafields and metabjects on that object. | | **Pricing** | The price is derived from the parent variant. 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. 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 Works without Liquid change Sellable quantity is available through Liquid | Multiple component variants App is responsible for its own variant picker on the product details page Sellable quantity is only available through the Storefront API | | **Cart add** | **Input**: Parent bundle variant Displayed as grouped in cart and checkout **Output fields**: In cart, potential to query `cart.line.components` | **Input**: Multiple component variants Displayed as grouped in cart and checkout **Output fields**: In cart, potential to query `cart.line.components` | | **Oversell protection** | **Always**: Shopify maintains sellable quantities on the parent bundle variant. The parent inventory quantity is the minimum of the component's inventory quantities. | **Storefront**: App maintains instock/out of stock for the parent. **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](https://shopify.dev/docs/apps/build/product-merchandising/bundles/add-customized-bundle-function) using Shopify Functions. * [Add a fixed bundle](https://shopify.dev/docs/apps/build/product-merchandising/bundles/add-fixed-bundle) using the GraphQL Admin API. ***