The official WhatsApp Business Cloud API cannot send messages to Channels or Groups, only one-to-one messages to opted-in recipients. There is no documented endpoint for it, and Meta has not announced one. Third-party providers and unofficial libraries can automate channels or groups through unofficial paths, but they carry a real risk of the business number being blocked for mass activity. If an agent needs broadcast-style reach, the supported route is template messages to many individual recipients, with opt-in captured first.

Context: Stack Overflow #78899979 (accepted answer): asks whether the official Cloud API can send to WhatsApp Channels and Groups, noting third-party providers claim to. The accepted answer says Meta's official API has no such feature, only direct messages, and unofficial libraries that do it risk the number being blocked.