Record and export MQTT messages

Enable disk history, load recorded messages and download a topic’s current history as JSON.

About 4 minutes · MQTT Viewer 1.2 · Web UI screenshots

Before you start

Connect to a test broker and subscribe to a topic with incoming messages. The screenshots use walkthrough/recorded/temperature.

1. Enable disk recording

Open the top-right Settings cog. Turn on Record history to disk, set a Disk budget (GB), then click Save. Recording applies to messages received while it is enabled.

Disk recording and the in-memory budget are separate settings.
Disk recording and the in-memory budget are separate settings. Full size (opens in a new tab)

2. Load recorded history

Receive a few messages, select their topic, then click Load recorded history below the timeline. Use the timeline to inspect the stored readings.

The topic panel can read recorded messages from disk.
Load recorded history sits below the timeline. Full size (opens in a new tab)

3. Export the topic

Right-click the topic in List and choose Export message history. In the web UI, the browser downloads a JSON file. Each entry includes its topic, payload, QoS, retain flag and arrival time.

Export message history is in the topic’s context menu.
Export message history is in the topic’s context menu. Full size (opens in a new tab)

What the export contains

Export uses the topic’s current in-memory history. Loading recorded history does not turn it into an export of the full disk archive. Disk and memory budgets can remove older entries, so keep the downloaded file if you need a separate copy.