Also known as: ADC
Application Default Credentials (ADC) are a Google Cloud mechanism for discovering authorization credentials that an application can use when calling Google APIs. ADC is designed for applications that should run with a consistent service identity, particularly in managed environments such as App Engine, Compute Engine, or similar deployments.
The Application Default Credentials (ADC) provide a simple way to get authorization credentials for use in calling Google APIs. They are best suited for cases when the call needs to have the same identity and authorization level for the application independent of the user. This is the recommended approach to authorize calls to Google Cloud APIs, particularly when you're building an application that is deployed to Google App Engine (GAE) or Compute Engine virtual machines. For more information, see How Application Default Credentials works.