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MQTT.fx vs mqtt-spy: catalog facts
MQTT.fx	mqtt-spy
Paid Commercial licence with a free trial.	Free Free and open source under the Eclipse Public License.
macOS	Windows, Command line
Tests broker connections without writing code Eclipse Sparkplug explorer and editor	Both a desktop interface and a headless daemon Focused on monitoring MQTT topic activity
Paid after the trial Free open-source MQTT clients cover basic use	No packaged releases on the GitHub repository Little recent development activity
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: EPL-1.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.