MQTT GeneralInstall

Summary

Publish a debug payload via MQTT to a specified topic, optionally including selected input fields and awaiting a response message on a separate topic.

Inputs

• Topic (required) — The MQTT topic to publish the debug payload to.
• QoS — The MQTT Quality of Service level for the published message (0, 1, or 2). Defaults to 1.
• Include Input Items — Whether to include chosen fields from the node's input items inside the payload under inputItems.
• Include Input Items Fields — Comma or newline-separated list of specific fields from the input items to include when 'Include Input Items' is enabled.
• Wait For Response — Whether to wait for a reply message on a specified response topic before finishing; disables immediate output.
• Response Topic (required) — The MQTT topic to listen on for the response message if 'Wait For Response' is enabled. Defaults to 'RES_' prepended to the publish topic.
• Response Timeout (ms) — Maximum time in milliseconds to wait for the response message. Defaults to 10,000 ms.
• Parse Response As JSON — Whether to parse the response payload as JSON if possible. Defaults to true.
• Debug Inputs — A set of optional debug fields that are serialized and included in the published payload, e.g., Debug Text, Debug Dropdown, Debug Number, Debug JSON, and others.

Output shape

a list of items matching the input length, each augmented with an mqtt property containing the published topic, action details, and payload; if 'Wait For Response' is enabled, includes the response topic, raw message, and parsed payload if received before timeout; if no input items are present, a single-item list is returned with the MQTT message details.

If 'Wait For Response' is enabled, the node subscribes to the specified response topic and waits for a response message up to the timeout period. The response is included in the output item(s) under mqtt.response. If no response is received within the timeout, the node throws an error or outputs an error item if 'Continue On Fail' is set. The published payload is a JSON string containing action metadata and the selected input fields under inputs.inputItems if configured.

Examples

Example 1: Publish a debug payload with default QoS and no response wait.

Topic set to "playwright/mouse/click",_includeInputItems=false, waitForResponse=false, and various optional debug fields set as desired.

Example 2: Publish a debug payload and wait for response on a related topic.

Topic set to "device/phone_01/action", waitForResponse=true, responseTopic set to "RES_device/phone_01/action", and adjusted response timeout and parse option.

Links

• n8n community nodes installation guide