> ## Documentation Index > Fetch the complete documentation index at: https://polar.sh/docs/llms.txt > Use this file to discover all available pages before exploring further. # Customer State > The quickest way to integrate billing in your application Customer State is a concept allowing you to query for the current state of a customer, including their active subscriptions and granted [benefits](/features/benefits/introduction), in a single [API call](/api-reference/customers/state-external) or single [webhook event](/api-reference/webhooks/customer.state_changed). Combined with the [External ID](/features/customer-management#external-id) feature, you can get up-and-running in minutes. ## The customer state object The customer state object contains: * All the data about the customer. * The list of their **active** subscriptions. * 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. One endpoint to rule them all, using your own customer ID. The same one, but with internal Polar customer ID. ## The `customer.state_changed` webhook To be notified of the customer state changes, you can listen to the `customer.state_changed` webhook event. It's triggered when: * Customer is created, updated or deleted. * A subscription is created or updated. * A benefit is granted or revoked. By subscribing to this webhook event, you keep your system up-to-date and update your customer's access accordingly. One webhook to rule them all.