If Speech-to-Text from a GCS URI returns 403 storage.objects.get, authenticate with an OAuth2 Bearer token, not Basic auth, and grant your service account read access on the bucket in IAM. Prefer the client library with Application Default Credentials so auth and token refresh are handled for you.

Context: Stack Overflow #56302658 (accepted answer, 31 votes): a user transcribing from a Google Cloud Storage URI got 403 Anonymous caller does not have storage.objects.get. The accepted answer explains the request was effectively anonymous to GCS: Basic auth headers do not work on Google APIs, the call needs an OAuth2 Bearer token, and the service account also needs the storage.objects.get permission on the bucket via IAM. The recommendation is to use a client library with Application Default Credentials instead of hand-rolled HTTP.