MQTT Monitor for Desktop
Observe your brokers.
Understand
your data.
MQTT-JS is a free, open-source desktop app for monitoring multiple MQTT brokers simultaneously with real-time protobuf message decoding.
What it does
Everything you need to inspect MQTT traffic
Built for developers and IoT engineers who need to understand what's happening on their message bus.
Multiple Brokers
Connect and monitor several MQTT brokers simultaneously from a single window. Each connection is managed independently with its own status indicator.
TLS / MQTTS
Full TLS support with CA certificate, client cert, and private key — including self-signed certificates and mutual TLS.
Protobuf Decoding
Load .proto files and map topic patterns to message types. Binary payloads are decoded automatically into human-readable JSON.
Topic Filtering
Filter the live message stream by topic substring or MQTT wildcards (+ and #). Save filters for quick reuse.
Persistent Config
Connections, proto files, topic mappings, and filters are saved and automatically restored across restarts.
Real-time Stream
Live message feed with pause/resume and a 10,000-message ring buffer. Never miss a message, never run out of memory.
Free & Open Source
Download MQTT-JS
Unpack, run. No installation wizard, no accounts, no cloud. Just a desktop app that works.