> ## Documentation Index
> Fetch the complete documentation index at: https://primer.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# start

```ts TS theme={"dark"}
start(): void
```

Start the Headless Checkout instance. Once the instance is started, the callback `onAvailablePaymentMethodsLoad` is called with the list of payment methods.

After calling this method, you can use the payment method managers returned by
[createPaymentMethodManager](/sdk/web/v2.x.x/primer-headless-checkout/methods/createPaymentMethodManager) to create and manage payments.

Also see the documentation on how to
[initialize a Headless Checkout](/checkout/headless#step-2%3A-initialize-primer’s-headless-universal-checkout).