---
search:
  tags:
    - URL Groups
    - POST
seo:
  description: >-
    Send a message to all endpoints in a URL group. Fan-out is a publish,…
    Reference for the POST /api/v2/url-groups/{groupId}/publish endpoint in the
    Anlyon API.
sidebar:
  label: Publish to all endpoints in a group
  badge: POST
title: Publish to all endpoints in a group
type: openapi-operation
---
Send a message to all endpoints in a URL group. Fan-out is a publish, so
it obeys the same rules as `POST /messages/publish`: the messages are
created in the calling key's environment, a halted environment refuses
an agent key's publish with `409`, and a `{{secret:NAME}}` reference in
a delivery header requires `secrets:read`.

Against a key budget the publish costs one unit per endpoint in the
group, and admission is all-or-nothing: a fan-out that does not fit the
remaining cap is refused whole with `429 BUDGET_EXCEEDED` and no
endpoint receives a message.

`POST /api/v2/url-groups/{groupId}/publish`