Purchase options extensions are a type of Admin UI extension that enable merchants to create and edit purchase options on the product and product variant page with an [admin action](/docs/apps/build/admin/actions-blocks#admin-actions) in the Shopify admin.
This guide introduces the purchase options extensions and how they work.

## How it works

The purchase options extensions is rendered on the product page and the product variant page, and allows merchants to add, remove, create, and edit selling plans from the purchase options card.

## Division of responsibilities between Shopify and apps

The division of responsibilities enables Shopify to provide a fully integrated purchase option experience and enables apps to provide innovative user-facing workflows and purchase option management automation.

The following table describes the division of responsibilities between Shopify and purchase options apps:

<table class="subscriptions-division-responsibilities">
  <caption>Division of responsibilities between Shopify and apps</caption>
  <thead>
    <tr>
      <th style="width:80vw">Responsibility</th>
      <th style="width:10vw">Shopify</th>
      <th style="width:10vw">App</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Add a product or product variant to an existing purchase option</td>
      <td>&#x2714;</td>
      <td></td>
    </tr>
    <tr>
      <td>Remove a product or product variant from an existing purchase option</td>
      <td>&#x2714;</td>
      <td></td>
    </tr>
    <tr>
      <td>Create a purchase option on a product or product variant page</td>
      <td></td>
      <td>&#x2714;</td>
    </tr>
    <tr>
      <td>Edit a purchase option from a product or product variant page</td>
      <td></td>
      <td>&#x2714;</td>
    </tr>
  </tbody>
</table>

App developers can refer to the [`selling_plan_groups/create`](/docs/api/webhooks?reference=toml#list-of-topics-selling_plan_groups/create) and [`selling_plan_groups/udpate`](docs/api/webhooks?reference=toml#list-of-topics-selling_plan_groups/update) webhooks to be informed when a subscription, pre-order, or try-before-you-buy (TBYB) option is getting updated.

> Note:
> Apps aren't required to create a purchase options extension. When merchants want to edit the purchase options, they will be redirected to the app when there is no extension available.

## How the extension renders in Shopify

Shopify renders a purchase options card on the product and product variant page, which contains a set of possible actions. Apps, when they want to use the Admin UI Extension, are responsible for the integration of the creation and the edition of the purchase options.

The following image shows how the purchase options card looks on the product or product variant page:

![Purchase options card](/assets/api/purchase-options/extension/purchase-options-card.png)

### Next steps

- [Start building a purchase options extension](/docs/apps/build/purchase-options/purchase-options-extensions/start-building).