---
title: "Publish a cross-server message to a universe"
method: POST
path: "/messaging-service/v1/universes/{universeId}/topics/{topic}"
tags: ["Universes"]
---

# Publish a cross-server message to a universe

`POST /messaging-service/v1/universes/{universeId}/topics/{topic}`

## Request

- Base URL: `https://apis.roblox.com`
- URL: `https://apis.roblox.com/messaging-service/v1/universes/{universeId}/topics/{topic}`
- Auth: one of:
  - API key in header `x-api-key`
  - OAuth 2
    - Authorization code: `https://apis.roblox.com/oauth/v1/authorize`
    - Token URL: `https://apis.roblox.com/oauth/v1/token`

Publish a message to a pre-defined topic of an experience, with the size of the message up to 1,024 characters (1 KB). Requires the **Publish** permission for API keys and the **universe-messaging-service:publish** scope for OAuth 2.0 apps. See [Cross-server messaging](/cloud-services/cross-server-messaging.md#subscribe-users-to-receive-messages) for defining and subscribing users to a topic.

## Path parameters

- `universeId` integer, required
- `topic` string, nullable, required

## Request body

- PublishRequest: The request body object with the message string that you want to publish to the live server.
  - `message` string, nullable: The message content that you want to publish to the live server.

## Response `200`

Returns an empty response body.

## Other responses

- `400`: Invalid request.
- `401`: The API key is not valid for this operation / You don't have the authorization.
- `403`: Publishing is not allowed on this experience.
- `500`: Server internal error / Unknown error.

---

[API](https://skmtc.dev/roblox/apis/roblox-api.md) - [All operations](https://skmtc.dev/roblox/apis/roblox-api/llms.txt) - [OpenAPI document](https://skmtc.dev/roblox/apis/roblox-api/revisions/bcfdc20689cd?raw)