@polar-sh/better-auth

A Better Auth plugin for integrating Polar payments and subscriptions into your authentication flow.

Features

- Checkout Integration
- Customer Portal
- Automatic Customer creation on signup
- Event Ingestion & Customer Meters for flexible Usage Based Billing
- Handle Polar Webhooks securely with signature verification
- Reference System to associate purchases with organizations

Installation

``bash
pnpm add better-auth @polar-sh/better-auth @polar-sh/sdk
`

Preparation

Go to your Polar Organization Settings, and create an Organization Access Token. Add it to your environment.

`bash


.env


POLAR_ACCESS_TOKEN=...
`

$3

The Polar plugin comes with a handful additional plugins which adds functionality to your stack.

- Checkout - Enables a seamless checkout integration
- Portal - Makes it possible for your customers to manage their orders, subscriptions & granted benefits
- Usage - Simple extension for listing customer meters & ingesting events for Usage Based Billing
- Webhooks - Listen for relevant Polar webhooks

`typescript
import { betterAuth } from "better-auth";
import { polar, checkout, portal, usage, webhooks } from "@polar-sh/better-auth";
import { Polar } from "@polar-sh/sdk";

const polarClient = new Polar({
accessToken: process.env.POLAR_ACCESS_TOKEN,
// Use 'sandbox' if you're using the Polar Sandbox environment
// Remember that access tokens, products, etc. are completely separated between environments.
// Access tokens obtained in Production are for instance not usable in the Sandbox environment.
server: 'sandbox'
});

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
client: polarClient,
createCustomerOnSignUp: true,
use: [
checkout({
products: [
{
productId: "123-456-789", // ID of Product from Polar Dashboard
slug: "pro" // Custom slug for easy reference in Checkout URL, e.g. /checkout/pro
}
],
successUrl: "/success?checkout_id={CHECKOUT_ID}",
authenticatedUsersOnly: true,
returnUrl: "https://myapp.com", // Optional Return URL, which renders a Back-button in the Checkout
}),
portal({
returnUrl: "https://myapp.com", // Optional Return URL, which renders a Back-button in the Customer Portal
}),
usage(),
webhooks({
secret: process.env.POLAR_WEBHOOK_SECRET,
onCustomerStateChanged: (payload) => // Triggered when anything regarding a customer changes
onOrderPaid: (payload) => // Triggered when an order was paid (purchase, subscription renewal, etc.)
... // Over 25 granular webhook handlers
onPayload: (payload) => // Catch-all for all events
})
],
})
]
});
`

$3

You will be using the BetterAuth Client to interact with the Polar functionalities.

`typescript
import { createAuthClient } from "better-auth/react";
import { polarClient } from "@polar-sh/better-auth";
import { organizationClient } from "better-auth/client/plugins";

// This is all that is needed
// All Polar plugins, etc. should be attached to the server-side BetterAuth config
export const authClient = createAuthClient({
plugins: [polarClient()],
});
`

Configuration Options

`typescript
import { betterAuth } from "better-auth";
import {
polar,
checkout,
portal,
usage,
webhooks,
} from "@polar-sh/better-auth";
import { Polar } from "@polar-sh/sdk";

const polarClient = new Polar({
accessToken: process.env.POLAR_ACCESS_TOKEN,
// Use 'sandbox' if you're using the Polar Sandbox environment
// Remember that access tokens, products, etc. are completely separated between environments.
// Access tokens obtained in Production are for instance not usable in the Sandbox environment.
server: "sandbox",
});

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
client: polarClient,
createCustomerOnSignUp: true,
getCustomerCreateParams: ({ user }, request) => ({
metadata: {
myCustomProperty: 123,
},
}),
use: [
// This is where you add Polar plugins
],
}),
],
});
`

$3

- client: Polar SDK client instance

$3

- createCustomerOnSignUp: Automatically create a Polar customer when a user signs up
- getCustomerCreateParams: Custom function to provide additional customer creation metadata

$3

When createCustomerOnSignUp is enabled, a new Polar Customer is automatically created when a new User is added in the Better-Auth Database.

All new customers are created with an associated externalId, which is the ID of your User in the Database. This allows us to skip any Polar <-> User mapping in your Database.

Checkout Plugin

To support checkouts in your app, simply pass the Checkout plugin to the use-property.

`typescript
import { polar, checkout } from "@polar-sh/better-auth";

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
...
use: [
checkout({
// Optional field - will make it possible to pass a slug to checkout instead of Product ID
products: [ { productId: "123-456-789", slug: "pro" } ],
// Relative URL to return to when checkout is successfully completed
successUrl: "/success?checkout_id={CHECKOUT_ID}",
// Optional Return URL, which renders a Back-button in the Checkout
returnUrl: "https://myapp.com",
// Wheather you want to allow unauthenticated checkout sessions or not
authenticatedUsersOnly: true,
// Enforces the theme - System-preferred theme will be set if left omitted
theme: "dark"
})
],
})
]
});
`

When checkouts are enabled, you're able to initialize Checkout Sessions using the checkout-method on the BetterAuth Client. This will redirect the user to the Product Checkout.

`typescript
await authClient.checkout({
// Any Polar Product ID can be passed here
products: ["e651f46d-ac20-4f26-b769-ad088b123df2"],
// Or, if you setup "products" in the Checkout Config, you can pass the slug
slug: "pro",
});
`

Checkouts will automatically carry the authenticated User as the customer to the checkout. Email-address will be "locked-in".

If authenticatedUsersOnly is false - then it will be possible to trigger checkout sessions without any associated customer.




$3

You can use the checkoutEmbed method to instead open the Checkout as an Embed on your site.

`typescript
const embed = await authClient.checkoutEmbed({
products: ["e651f46d-ac20-4f26-b769-ad088b123df2"],
});

// Listen for successful completion
checkout.addEventListener("success", (event) => {
console.log("Purchase successful!", event.detail);

// Call event.preventDefault() if you want to prevent the standard behavior
// event.preventDefault()
// Note: For success event, this prevents automatic redirection if redirect is true

// If redirect is false, you can show your own success message
if (!event.detail.redirect) {
showSuccessMessage();
}
// Otherwise, the user will be redirected to the success URL (unless prevented)
});
`

$3

This plugin supports the Organization plugin. If you pass the organization ID to the Checkout referenceId, you will be able to keep track of purchases made from organization members.

`typescript
const organizationId = (await authClient.organization.list())?.data?.[0]?.id,

await authClient.checkout({
// Any Polar Product ID can be passed here
products: ["e651f46d-ac20-4f26-b769-ad088b123df2"],
// Or, if you setup "products" in the Checkout Config, you can pass the slug
slug: 'pro',
// Reference ID will be saved as referenceId in the metadata of the checkout, order & subscription object
referenceId: organizationId
});
`

Portal Plugin

A plugin which enables customer management of their purchases, orders and subscriptions.

`typescript
import { polar, checkout, portal } from "@polar-sh/better-auth";

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
...
use: [
checkout(...),
portal({
// Optional Return URL, which renders a Back-button in the Customer Portal
redirectUrl: "https://myapp.com"
})
],
})
]
});
`

The portal-plugin gives the BetterAuth Client a set of customer management methods, scoped under authClient.customer.

$3

The following method will redirect the user to the Polar Customer Portal, where they can see orders, purchases, subscriptions, benefits, etc.

`typescript
await authClient.customer.portal();
`

$3

The portal plugin also adds a convenient state-method for retrieving the general Customer State.

`typescript
const { data: customerState } = await authClient.customer.state();
`

The customer state object contains:

- All the data about the customer.
- The list of their active subscriptions
- Note: This does not include subscriptions done by a parent organization. See the subscription list-method below for more information.
- The list of their granted benefits.
- The list of their active meters, with their current balance.

Thus, with that single object, you have all the required information to check if you should provision access to your service or not.

You can learn more about the Polar Customer State in the Polar Docs.

$3

The portal plugin adds 3 convenient methods for listing benefits, orders & subscriptions relevant to the authenticated user/customer.

All of these methods use the Polar CustomerPortal APIs

#### Benefits

This method only lists granted benefits for the authenticated user/customer.

`typescript
const { data: benefits } = await authClient.customer.benefits.list({
query: {
page: 1,
limit: 10,
},
});
`

#### Orders

This method lists orders like purchases and subscription renewals for the authenticated user/customer.

`typescript
const { data: orders } = await authClient.customer.orders.list({
query: {
page: 1,
limit: 10,
productBillingType: "one_time", // or 'recurring'
},
});
`

#### Subscriptions

This method lists the subscriptions associated with authenticated user/customer.

`typescript
const { data: subscriptions } = await authClient.customer.subscriptions.list({
query: {
page: 1,
limit: 10,
active: true,
},
});
`

Important - Organization Support

This will not return subscriptions made by a parent organization to the authenticated user.

However, you can pass a referenceId to this method. This will return all subscriptions associated with that referenceId instead of subscriptions associated with the user.

So in order to figure out if a user should have access, pass the user's organization ID to see if there is an active subscription for that organization.

`typescript
const organizationId = (await authClient.organization.list())?.data?.[0]?.id,

const { data: subscriptions } = await authClient.customer.subscriptions.list({
query: {
page: 1,
limit: 10,
active: true,
referenceId: organizationId
},
});

const userShouldHaveAccess = subscriptions.some(
sub => // Your logic to check subscription product or whatever.
)
`

Usage Plugin

A simple plugin for Usage Based Billing.

`typescript
import { polar, checkout, portal, usage } from "@polar-sh/better-auth";

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
...
use: [
checkout(...),
portal(),
usage()
],
})
]
});
`

$3

Polar's Usage Based Billing builds entirely on event ingestion. Ingest events from your application, create Meters to represent that usage, and add metered prices to Products to charge for it.

Learn more about Usage Based Billing in the Polar Docs.

`typescript
const { data: ingested } = await authClient.usage.ingest({
event: "file-uploads",
metadata: {
uploadedFiles: 12,
},
});
`

The authenticated user is automatically associated with the ingested event.

$3

A simple method for listing the authenticated user's Usage Meters, or as we call them, Customer Meters.

Customer Meter's contains all information about their consumtion on your defined meters.

- Customer Information
- Meter Information
- Customer Meter Information
- Consumed Units
- Credited Units
- Balance

`typescript
const { data: customerMeters } = await authClient.usage.meters.list({
query: {
page: 1,
limit: 10,
},
});
`

Webhooks Plugin

The Webhooks plugin can be used to capture incoming events from your Polar organization.

`typescript
import { polar, webhooks } from "@polar-sh/better-auth";

const auth = betterAuth({
// ... Better Auth config
plugins: [
polar({
...
use: [
webhooks({
secret: process.env.POLAR_WEBHOOK_SECRET,
onCustomerStateChanged: (payload) => // Triggered when anything regarding a customer changes
onOrderPaid: (payload) => // Triggered when an order was paid (purchase, subscription renewal, etc.)
... // Over 25 granular webhook handlers
onPayload: (payload) => // Catch-all for all events
})
],
})
]
});
`

Configure a Webhook endpoint in your Polar Organization Settings page. Webhook endpoint is configured at /polar/webhooks.

Add the secret to your environment.

`bash


.env


POLAR_WEBHOOK_SECRET=...
`

The plugin supports handlers for all Polar webhook events:

- onPayload - Catch-all handler for any incoming Webhook event
- onCheckoutCreated - Triggered when a checkout is created
- onCheckoutUpdated - Triggered when a checkout is updated
- onOrderCreated - Triggered when an order is created
- onOrderPaid - Triggered when an order is paid
- onOrderRefunded - Triggered when an order is refunded
- onRefundCreated - Triggered when a refund is created
- onRefundUpdated - Triggered when a refund is updated
- onSubscriptionCreated - Triggered when a subscription is created
- onSubscriptionUpdated - Triggered when a subscription is updated
- onSubscriptionActive - Triggered when a subscription becomes active
- onSubscriptionCanceled - Triggered when a subscription is canceled
- onSubscriptionRevoked - Triggered when a subscription is revoked
- onSubscriptionUncanceled - Triggered when a subscription cancellation is reversed
- onProductCreated - Triggered when a product is created
- onProductUpdated - Triggered when a product is updated
- onOrganizationUpdated - Triggered when an organization is updated
- onBenefitCreated - Triggered when a benefit is created
- onBenefitUpdated - Triggered when a benefit is updated
- onBenefitGrantCreated - Triggered when a benefit grant is created
- onBenefitGrantUpdated - Triggered when a benefit grant is updated
- onBenefitGrantRevoked - Triggered when a benefit grant is revoked
- onCustomerCreated - Triggered when a customer is created
- onCustomerUpdated - Triggered when a customer is updated
- onCustomerDeleted - Triggered when a customer is deleted
- onCustomerStateChanged` - Triggered when a customer is created