Set Up App-Only Authentication for SharePoint Online With Tenant Permissions

Access the registration form of the site collection to crawl. The format is:

Select Generate to the right of the Client ID field.

Select Generate to the right of the Client Secret field.

Enter an application name value in the Title field.

Enter the domain value in the App Domain field.

Enter a URL value in the Redirect URI field.

Select Create to register the application.

Copy or write down the information in the Save APP information summary fields and store it in a secure location.

Access the admin Permissions page of the site collection to crawl. The format is :

Enter the Client ID into the App ID field.

Select Lookup.

Verify the values automatically populated in the following fields are accurate.

Enter the following in the Permissions Request XML field.

<AppPermissionRequests AllowAppOnlyPolicy="true">
  <AppPermissionRequest Scope="http://sharepoint/content/tenant" Right="FullControl" />
</AppPermissionRequests>

Select Create.

In the Trust new App window, select Trust It.