What type of OAuth Client ID should you use to authenticate an application writing files to Google Drive?

Using an OAuth Client ID with the https://www.googleapis.com/auth/drive.file scope is appropriate for an application that needs to write files to Google Drive because this scope specifically allows the application to create or manipulate files that it has created or opened with that authorization. This means the application will have access to only those files, ensuring better security and control over what the application can access within a user's Google Drive.

This granular access is crucial because it limits the application’s permissions, adhering to the principle of least privilege, which is a best practice in security. By only granting access to the specific files the application needs, it mitigates the risk of unauthorized access to the user’s other files and sensitive information stored in their Google Drive.

In contrast, other options might provide broader access or involve more complex setups that are not necessary for simple file writing tasks. Using delegated domain-wide authority or service accounts can be more suitable for applications that need to impersonate users across a domain rather than for single-user, application-specific access to files.