## Initialize embedded Checkout

This method initializes embedded Checkout.

This method returns a `Promise` which resolves with an embedded Checkout instance.

**Syntax:** `stripe.initEmbeddedCheckout(...)`

- `options` (object) **required**
  Embedded Checkout initialization options.

  - `fetchClientSecret` (function) **required**
    A callback function `fetchClientSecret() => Promise<string>` that resolves with the [client secret](/api/checkout/sessions/object.md#checkout_session_object-client_secret) for the [Checkout Session](docs/api/checkout/sessions/object).

  - `clientSecret (deprecated)` (string) **required**
    _This param has been deprecated in favor of the `fetchClientSecret` param, which offers a faster loading experience._

The [client secret](/api/checkout/sessions/object.md#checkout_session_object-client_secret) for the [Checkout Session](docs/api/checkout/sessions/object).

  - `onComplete` (function)
    An optional callback function `onComplete() => void` that is called on completion for Checkout Sessions with `redirect_on_completion: if_required`.

### Initialize embedded Checkout

```es_next
const fetchClientSecret = async () => {
  const clientSecret = await createCheckoutSession();
  return clientSecret;
};

const checkout = await stripe.initEmbeddedCheckout({
  fetchClientSecret,
});
```