Gmail vs Instatus

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.

Instatus's REST API (`api.instatus.com`) lets a status-page owner script incident and maintenance updates, component status changes, and subscriber management for their own hosted status page. Every request must carry an `Authorization: Bearer <API_KEY>` header and a page ID from the dashboard, confirmed live via a 401 "API key is not sent in request header" response on an unauthenticated GET to `/v1/pages`; the same endpoint echoes a matching `access-control-allow-origin` on both a GET and a separate OPTIONS preflight sent with an Origin header, confirming the API is browser-callable. Instatus itself runs a permanent free-forever plan alongside paid per-project tiers, with no separate gate on API access.