Loads credentials from a file identified via a search strategy known as Application Default Credentials (ADC). The hope is to make auth "just work" for someone working on Google-provided infrastructure or who has used Google tooling to get started, such as the gcloud command line tool.

A sequence of paths is consulted, which we describe here, with some abuse of notation. ALL_CAPS represents the value of an environment variable and %||% is used in the spirit of a null coalescing operator.

# on Windows:
(APPDATA %||% SystemDrive %||% C:)\gcloud\application_default_credentials.json
# on not-Windows:

If the above search successfully identifies a JSON file, it is parsed and ingested as a service account, an external account ("workload identity federation"), or a user account. Literally, if the JSON describes a service account, we call credentials_service_account() and if it describes an external account, we call credentials_external_account().

credentials_app_default(scopes = NULL, ..., subject = NULL)



A character vector of scopes to request. Pick from those listed at https://developers.google.com/identity/protocols/oauth2/scopes.

For certain token flows, the "https://www.googleapis.com/auth/userinfo.email" scope is unconditionally included. This grants permission to retrieve the email address associated with a token; gargle uses this to index cached OAuth tokens. This grants no permission to view or send email and is generally considered a low-value scope.


Additional arguments passed to all credential functions.


An optional subject claim. Use for a service account which has been granted domain-wide authority by an administrator. Such delegation of domain-wide authority means that the service account is permitted to act on behalf of users, without their consent. Identify the user to impersonate via their email, e.g. subject = "user@example.com".


if (FALSE) {