Debug and test MQTT in seconds
MQTT Viewer is a free, open-source MQTT client for macOS, Windows, and Linux. Connect to multiple brokers at once, watch topics update live, decode payloads, and re-publish messages — with full MQTT v3.1.1 and v5 support.
Free & open-source (GPL-3.0) · macOS, Windows & Linux
Why use MQTT Viewer?
Everything you need to inspect, debug, and test MQTT — in one fast, native app that stays out of your way.
- Connect to up to 10 MQTT brokers at the same time
- Full MQTT v3.1.1 and v5 support, including v5 publish headers
- Secure connections over TCP, TLS/SSL, mutual TLS (client certificates) and WebSocket (ws/wss)
- Username & password authentication
- Live topic tree to visualize an entire broker at a glance
- Interactive message timeline to scrub through history
- Message comparison to diff payloads over time
- Sparkplug B (protobuf), Base64 and Hex payload decoding
- Free-text and pattern-based message filtering
- Publish messages and re-send them from a searchable publish history
Unlike existing apps, it's intuitive, snappy, and includes all of the features I could want in a client. It's by far the most responsive MQTT client out there.
Christophe De Troyer
Founder, Loomy
Debug all your environments
Connect to up to 10 MQTT brokers at once and switch between development, staging, and production without juggling windows.
Download nowRepublish common messages
Format, encode, and decode payloads with built-in Sparkplug B, Base64, and Hex codecs. Quickly re-publish past messages from a searchable history.
Download nowNever miss a message
Powerful free-text and pattern filtering plus an interactive timeline make it easy to find exactly the data you're looking for.
Download nowLoved by engineers ❤️
MQTT Viewer makes debugging my ESP32 projects so easy. Real-time monitoring and zero hassle. It’s become an essential tool in my workflow.
Mair Swartz
Creator, LearnESP32.com
Our developers love MQTT Viewer. It’s fast, intuitive, and is now indispensable. Easily the best MQTT client out there.
Mike Thompson
Founder, HackHunter
Frequently asked questions
Is MQTT Viewer free?
Yes. MQTT Viewer is completely free and open-source under the GPL-3.0 license. There are no paid tiers, trials, accounts, or sign-ups — every feature is available at no cost.
Is MQTT Viewer open source?
Yes. The full source code is published on GitHub under the GPL-3.0 license at github.com/mqtt-viewer/mqtt-viewer, so you can read, build, and contribute to it.
Which platforms does MQTT Viewer run on?
MQTT Viewer is a native desktop application for macOS (Apple Silicon and Intel), Windows, and Linux (x86_64 and ARM64).
Does MQTT Viewer support MQTT 5?
Yes. MQTT Viewer supports both MQTT v3.1.1 and MQTT v5, including publishing messages with MQTT v5 properties and headers.
Does MQTT Viewer support TLS, WebSocket, and client certificates?
Yes. You can connect over plain TCP, TLS/SSL, mutual TLS with client certificates, and WebSocket (ws/wss), with username and password authentication.
Can I connect to more than one broker at the same time?
Yes. MQTT Viewer supports up to 10 simultaneous broker connections, so you can monitor and switch between development, staging, and production environments instantly.
See the full FAQ for more.