> For the complete documentation index, see [llms.txt](https://docs.thingsup.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.thingsup.io/actions/publish-mqtt-message-action.md).

# Publish MQTT Message Action

This provides a way to publish message to MQTT Broker. Before adding Publish MQTT Message Action, user has to define a [**MQTT Connection**](/connections/mqtt-connection.md). User need to provide following parameters to publish message to MQTT Broker.

#### PublishTopic

*  User need to provide MQTT Topic on which data will be published.

#### QoS

MQTT QoS value. Default is 1.

#### Function

* Javascript code to build mqtt message.
* "topic","message" and "payload" objects are available in this code, function can be used to set message body and topic from payload before sending to MQTT.
* Setting topic here overrides already defined PublishTopic.

```
//Example 1

message = payload;
topic = "somenewtopic";
```

#### Connection ID

User need to provide a Connection ID of MQTT connection.

![Add Publish MQTT Message Action](/files/BBDh5yktsSMBbKi38KKB)

Please note the following points:

{% hint style="info" %}

* "payload" object is supplied from Action Trigger like Rules, Action Command etc.
  {% endhint %}