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

# Start OAuth Flow

> Start an OAuth authentication flow using the Stytch Next.js SDK

`oauth.$provider.start()` kicks off an OAuth flow by redirecting the browser to one of Stytch's [OAuth Start](/docs/api-reference/b2b/api/oauth/organization/start-google) endpoints. One of `organization_id` or `slug` is required to specify which organization the user is trying to access. If the organization that the user is trying to access is not yet known, use the `oauth.$provider.discovery.start()` method instead.

The method will also generate a PKCE `code_verifier` and store it in local storage on the device (See the [PKCE OAuth guide](multi-tenant-auth/authentication/oauth/adding-pkce) for details). If your application is configured to use a custom subdomain with Stytch, it will be used automatically.

Use one of the following methods to start an OAuth flow:

* `oauth.google.start()`
* `oauth.microsoft.start()`
* `oauth.hubspot.start()`
* `oauth.slack.start()`
* `oauth.github.start()`

### Parameters

<ParamField path="organization_id" type="string">
  The id of the Organization to start the OAuth flow for.

  One of either `organization_id` or `slug` is required.
</ParamField>

<ParamField path="slug" type="string">
  The unique URL slug of the Organization. The slug only accepts alphanumeric characters and the following reserved characters: `-` `.` `_` `~`. Must be between 2 and 128 characters in length.

  One of either `organization_id` or `slug` is required.
</ParamField>

<ParamField path="login_redirect_url" type="string">
  The URL Stytch redirects to after the OAuth flow is completed for a Member that already exists. This URL should be a route in your application which will run oauth.authenticate (see below) and finish the login.

  The URL must be configured as a Login URL in the [Redirect URL page](https://stytch.com/dashboard/redirect-urls). If the field is not specified, the default Login URL will be used.
</ParamField>

<ParamField path="signup_redirect_url" type="string">
  The URL Stytch redirects to after the OAuth flow is completed for a Member that does not yet exist. This URL should be a route in your application which will run oauth.authenticate (see below) and finish the login.

  The URL must be configured as a Signup URL in the [Redirect URL page](https://stytch.com/dashboard/redirect-urls). If the field is not specified, the default Signup URL will be used.
</ParamField>

<ParamField path="custom_scopes" type="string">
  A space-separated list of custom scopes that you'd like to include. Note that this list must be URL encoded (e.g. the spaces must be expressed as %20).
</ParamField>

<ParamField path="provider_params" type="object">
  An object containing parameters that you'd like to pass along to the OAuth provider. For example, some OAuth providers support a `login_hint` parameter that allows you to pre-populate the OAuth login flow with a suggested email address. We recommend consulting each OAuth provider's documentation for a list of supported parameters. The keys in the `provider_params` object are the parameter names (like `login_hint`), and their values are the data that you'd like to pass along for each parameter (like `example_hint@stytch.com`).
</ParamField>

<Panel>
  <RequestExample>
    ```jsx theme={null}
    import { useStytchB2BClient } from '@stytch/nextjs/b2b';

    export const GoogleLogin = () => {
      const stytch = useStytchB2BClient();

      const startOAuth = () => {
        stytch.oauth.google.start({
          organization_id: 'organization-test-07971b06-ac8b-4cdb-9c15-63b17e653931',
          login_redirect_url: 'https://example.com/authenticate',
          signup_redirect_url: 'https://example.com/authenticate',
        });
      };

      return <button onClick={startOAuth}>Sign in with Google</button>;
    };
    ```
  </RequestExample>
</Panel>