Gmail vs Google Analytics

The Gmail API gives OAuth-scoped programmatic access to a user's mailbox: reading, searching, sending, and organizing messages, threads, labels, and drafts, with message bodies transported as base64url-encoded MIME inside JSON. It requires a Google OAuth 2.0 bearer token, confirmed live via a `WWW-Authenticate: Bearer realm="https://accounts.google.com/"` challenge on an unauthenticated request, and unlike most server-side email APIs it explicitly supports cross-origin browser calls, echoing the request Origin on both a GET and an OPTIONS preflight.

The Google Analytics 4 Data API (`analyticsdata.googleapis.com/v1beta`) lets applications pull custom reports of metrics, dimensions, and audience segments out of a GA4 property, complementing a separate Admin API used to manage properties, streams, and access. It requires a Google OAuth 2.0 bearer token, confirmed live via a `WWW-Authenticate: Bearer realm="https://accounts.google.com/"` challenge on an unauthenticated `runReport` call, and the same request repeated with an Origin header echoed `access-control-allow-origin` back, resolving CORS support from unknown to yes. The core Data API is free to call within Google's standard quotas, with Google Analytics 360 offered as a paid enterprise tier for higher limits and additional features.