Checkout Sessions are a fundamental part of Flowglad, representing a time-limited state that captures the necessary details to complete purchases, pay invoices, or add payment methods. They manage the state between initiating a checkout and its successful completion. By default, a Checkout Session is valid for 24 hours. If not completed within this timeframe, it will expire and can no longer be used.

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Checkout Session Types

Flowglad offers four distinct types of checkout sessions, each tailored to different scenarios:

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Product Checkout Session

A “product” checkout session is the most straightforward. The customer will checkout according to the standard terms defined on your product and price records. Customers can initiate these sessions directly by visiting a product or price purchase page. This type is ideal for scenarios where the customer doesn’t need to be logged in to your product (e.g. for services), and the transaction is for a standard product offering.

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Add Payment Method Checkout Session

The “Add Payment Method” checkout session provides a flow for customers to securely save a payment method to their Flowglad profile. Upon successful completion, the payment method is stored. Optionally, if a targetSubscriptionId is provided when creating the session, the newly added payment method will automatically become the default payment method for that specific subscription.

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Invoice Checkout Session

Invoice checkout sessions are used for settling payments for manually created Invoices. This is particularly useful for one-off transactions, add-ons, or scenarios where the exact amount due isn’t known until the invoice is raised. It allows customers to pay invoices that might not be tied to a predefined product or subscription.

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Creating a Checkout Session

You can initiate checkout sessions programmatically, most commonly using the useBilling() hook in your frontend application.

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Using useBilling() Hook

The createCheckoutSession method provided by the useBilling() hook is the primary way to create ProductCheckoutSessions or PurchaseCheckoutSessions. Here’s an example of how you might use it in a React component: 
import { useBilling } from '@flowglad/nextjs' // Also exported from @flowglad/react

// Inside your component
const { createCheckoutSession, loading, error } = useBilling()

const handleCheckout = async (product) => {
  try {
    await createCheckoutSession({
      priceId: product.defaultPrice.id, // Or a specific price ID
      successUrl: `${window.location.origin}/checkout-success`, // Your success page
      cancelUrl: window.location.href, // Where to return on cancellation
      quantity: 1,
      autoRedirect: true, // Automatically redirect to Flowglad Checkout after creation
      type: 'product',
    })
  } catch (err) {
    console.error("Failed to create checkout session:", err)
    // Handle error appropriately
  }
}
When creating a session, you can specify a successUrl and a cancelUrl. The customer will be redirected to the successUrl after a successful payment or to the cancelUrl if they abandon the session. If no successUrl is provided, Flowglad will redirect the user to a Flowglad-hosted success page.

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Creating an “Add Payment Method” Session

For creating AddPaymentMethod CheckoutSessions specifically, you can utilize the createAddPaymentMethodCheckoutSession function available through the useBilling hook. This function is tailored for scenarios where the primary goal is to securely capture and store a customer’s payment details. 
import { useBilling } from '@flowglad/nextjs' // Also exported from @flowglad/react

// Inside your component
const { createAddPaymentMethodCheckoutSession, loading, error } = useBilling()

const handleAddPaymentMethod = async () => {
  try {
    await createAddPaymentMethodCheckoutSession({
      successUrl: window.location.href, // Redirect back here on success
      cancelUrl: window.location.href, // Redirect back here on cancel
      autoRedirect: true, // Automatically redirect to Flowglad Checkout
      // Optionally, provide targetSubscriptionId to link the new method
      // targetSubscriptionId: 'sub_xxxxxx'
    })
  } catch (err) {
    console.error("Failed to create add payment method session:", err)
    // Handle error appropriately
  }
}

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Customer Association

When creating checkout sessions via API, you must provide a customerExternalId when creating a checkout session, especially if Flowglad is integrated as the payment layer within your application. Associating a checkout session with an existing customer record ensures that all billing activities are correctly attributed and avoids potential data discrepancies or the creation of duplicate customer profiles. While anonymous checkouts are possible (typically through hosted product/price pages), linking checkouts to existing customer records via customerExternalId is more robust, and is required for API-first integrations.