Every request your application sends to the Google Calendar API must include an authorization token. The token also identifies your application to Google.
About authorization protocols
Authorizing requests with OAuth 2.0
All requests to the Google Calendar API must be authorized by an authenticated user.
The details of the authorization process, or "flow," for OAuth 2.0 vary somewhat depending on what kind of application you're writing. The following general process applies to all application types:
- When you create your application, you register it using the Google Developers Console. Google then provides information you'll need later, such as a client ID and a client secret.
- Activate the Google Calendar API in the Google Developers Console. (If the API isn't listed in the Developers Console, then skip this step.)
- When your application needs access to user data, it asks Google for a particular scope of access.
- Google displays a consent screen to the user, asking them to authorize your application to request some of their data.
- If the user approves, then Google gives your application a short-lived access token.
- Your application requests user data, attaching the access token to the request.
- If Google determines that your request and the token are valid, it returns the requested data.
Some flows include additional steps, such as using refresh tokens to acquire new access tokens. For detailed information about flows for various types of applications, see Google's OAuth 2.0 documentation.
Here's the OAuth 2.0 scope information for the Google Calendar API:
||read/write access to Calendars|
||read-only access to Calendars|
To request access using OAuth 2.0, your application needs the scope information, as well as information that Google supplies when you register your application (such as the client ID and the client secret).
Tip: The Google APIs client libraries can handle some of the authorization process for you. They are available for a variety of programming languages; check the page with libraries and samples for more details.
Perform Google Apps Domain-Wide Delegation of Authority
In enterprise applications you may want to programmatically access users data without any manual authorization on their part. In Google Apps domains, the domain administrator can grant to third party applications domain-wide access to its users' data — this is referred as domain-wide delegation of authority. To delegate authority this way, domain administrators can use service accounts with OAuth 2.0.
For additional detailed information, see Using OAuth 2.0 for Server to Server Applications