MQTT client memory use and history limits

MQTT Viewer keeps history inside a per-connection memory budget and can record to disk within a separate budget.

The settings dialog showing the memory budget per connection, the current history memory use and the estimated total for one, two and three connections

Memory budget and disk budget

  • Memory budget: what each connection holds in RAM. 512 MB by default.
  • Disk budget: the optional durable store. Recording is off by default.

What the settings show

The settings dialog shows what history is using now. With recording on, the timeline pages back through everything recorded.

Behaviour under heavy load

Arriving messages are queued and drained in fixed batches, so a flood cannot back up into the interface. The app is tested against two brokers each pushing 2,000 messages a second.

Frequently asked questions

How much memory does MQTT Viewer use?

History is bounded by a per-connection budget, 512 MB by default. The settings dialog shows the live figure.

Related features

MQTT Viewer is free and open source, and runs on macOS, Windows and Linux.

Download MQTT Viewer