> ## Documentation Index
> Fetch the complete documentation index at: https://supertab-feature-merchant-auth-change-again.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Making a Purchase

> Purchase a pre-defined Offering using the Customer API

<Note>
  We strongly recommend you interact with the Customer API using Supertab.js
  when building integrations with Supertab.

  [Supertab.js](/supertab.js) deals with authentication, purchase confirmation, and payments for you and ensures that
  customers have the correct user experience.
</Note>

<Steps>
  <Step title="Authenticate your customer">
    Begin an <a href="./authentication">oauth flow</a> to obtain a bearer token for your customer.

    You must have a token for an authenticated customer before attempting to make a purchase.
  </Step>

  <Step title="Retrieve the current Website">
    Before being able to purchase an offering you must first know its ID and which currency your customer uses.
    The <a href="./endpoints/retrieve-site">Website</a> contains information on which offerings are available for sale,
    and their prices in your customer's current currency.

    If you have already retrieved the current Website before authenticating your customer it is important
    you re-fetch this information, as pricing details may have changed.
  </Step>

  <Step title="Purchase the offering">
    <a href="./endpoints/purchase-an-offering">Purchase</a> the offering in the correct currency to place it on your customer's tab.

    The response includes any resulting purchase and details of what action is required (if any) to complete the purchase.

    Purchases may be created in a `pending` state when further action is required. This is usually a payment
    from the customer.

    <Note>
      Supertab does not prevent customers from making purchases with duplicative entitlements,
      you should check for prior entitlement before making any purchase and be careful not to send
      multiple purchase requests simultaneously
    </Note>
  </Step>

  <Step title="Check purchase status">
    If a purchase has been created in a `pending` state
    you may poll for the <a href="./endpoints/retrieve-a-purchase">status of the purchase</a>.

    This is useful when you expect the purchase to complete soon (e.g you have already opened a payment popup)
    and need to perform some action after successful purchase immediately within the browser.

    You can also check purchase status through the Merchant API (when checking from a backend),
    by subscribing to a webhook, or by opener messages from checkout.supertab.co
  </Step>
</Steps>