Application Default

Application Default Credentials (ADC) simplify authentication for Google Cloud services.

Application Default Credentials (ADC) provide a strategy for authenticating applications to Google Cloud services. This mechanism automatically discovers credentials based on the execution environment (e.g., service account in Google Cloud, user credentials locally). It eliminates the need for explicit credential file paths, streamlining development and deployment across various Google Cloud platforms like Compute Engine, Google Kubernetes Engine, and Cloud Functions. ADC supports multiple credential types, ensuring secure and flexible access to APIs.

https://cloud.google.com/docs/authentication/production#applications