Question

I would like to use the Google OAuth sign in method, as Stack Overflow does.

But according to the OAuth 2.0 for client-side web applications the scope parameter is required.

    scope   (required) URL identifying the Google service to be accessed. 
See the documentation for the API you'd like to use for what scope to specify. 
To specify more than one scope, list each one separated with a space.

So what scope does Stack Overflow use?

    Stackoverflow.com is asking for some information from your Google Account.
 To see and approve the request, sign in.

Answer 1

StackOverflow uses OpenId.