This document is an overview of how authentication, authorization,
and accounting are accomplished.
For all API calls, your application needs to be authenticated.
When an API accesses a user's private data, your application
must also be authorized by the user to access the data.
For example, accessing a public Google+ post would not require user authorization,
but accessing a user's private calendar would.
Also, for quota and billing purposes, all API calls involve accounting.
This document summarizes the protocols used by Google APIs and provides links to more information.

## Access types

Read more in the [Authentication and authorization](https://developers.google.com/api-client-library/dotnet/get_started#auth) section in the Get Started page.

## Using API keys


More information and examples for API keys are provided on the
[API Keys](https://developers.google.com/api-client-library/dotnet/guide/aaa_apikeys)
page.

## Using OAuth 2.0


More information and examples for OAuth 2.0 are provided on the
[OAuth 2.0](https://developers.google.com/api-client-library/dotnet/guide/aaa_oauth)
page.