A number of tools make it simple to publish or subscribe on MQTT topics. Some are web-based, others are desktop.

• MQTT Board - diagnostic oriented MQTT 5.0 client tool based on mqtt.js. Available in open source.

• MQTT over websockets (experimental) - from the mosquitto project.

• HiveMQ Websockets Client - a websocket based client for your browser which supports publishing & subscribing.

• mqtt-svg-dash - SVG "live" dashboard from MQTT.

• mqtt-panel - a web interface for MQTT.

• ThingStudio - ThingStudio allows you create real-time HTML5 user interfaces for MQTT devices by writing simple HTML templates.

• Moquette - an open source JAVA broker for MQTT protocol.

• IOTSIM.IO - SaaS MQTT lab for web-based MQTT testing.

• MQTT WebSocket Toolkit - MQTT WebSocket Toolkit adopts the form of chat interface, simplifies the page operation logic, and facilitates users to test and verify MQTT application scenarios quickly.

• MQTT.Cool Test Client - A web interface for testing interaction between MQTT.Cool and any MQTT broker.

• MQTT on Android

• MQTT on iOS

• MQTT Explorer - MQTT client to visualize, publish, subscribe, plot topics. Visualizes topics in a topic hierarchy. Intended for service integration, maintenance and refactorings.

• TT3 - a full featured windows MQTT client application using Paho libs. Several additional features like performance testing and alerts.

• mqtt-spy - the most advanced open source utility for monitoring activity on MQTT topics; based on the Paho Java client; for details see the project's home page.

• MQTT.fx - MQTT.fx is a MQTT Client written in Java based on Eclipse Paho.

• mqtt-stats - MQTT Topic Statistics

• MQTT X - MQTT X is a cross-platform MQTT desktop client open sourced by EMQ, which supports macOS, Linux, and Windows. MQTT X adopts the form of chat interface, which simplifies the page operation, facilitates the user to quickly test the MQTT/MQTTS connection, publish and subscribe to MQTT messages.

• mosquitto_pub/mosquitto_sub - Publish/Subscribe command line clients, provided with the mosquitto package.

• mqtt-spy-daemon - a headless (command-line) version of mqtt-spy; for details see the project's home page.

• MIMIC MQTT Simulator - Thousands of publishers and/or subscribers for rapid prototyping of IoT Applications, performance testing and tuning of deployments.

• Bevywise IoT Simulator - IoT Simulator provides complete functional and performance testing tools for the MQTT Platform, Application & Devices Development.

• IA92 - IA92 support pack includes very useful MQTT Java swing GUI for publishing & subscribing.

• OS X desktop notifications using Growl.

• Ubuntu desktop notifications using pynotify.

• Zenity notifications for MQTT messages.

• Desktop notifications for MQTT messages with DBUS.

• Desktop notifications with libnotify.

• Xenqtt - includes a client library, mock broker for unit/integration testing, and applications to support enterprise needs like using a cluster of servers as a single client, an HTTP gateway, etc.

• twitter2mqtt - a Twitter to MQTT gateway (1-shot) which is using mosquitto.

• mqtt-http-bridge - this simple web application provides a bridge between HTTP and MQTT using a RESTish interface.

• mqtt-to-twitter-daemon - a MQTT to Twitter ruby daemon.

• twitter-to-mqtt-daemon - a Twitter User-streams to MQTT ruby daemon.

• mqtt-republisher-daemon - a small MQTT topics republisher.

• OPC Router - MQTT Gateway (publisher/subscriber) with various plug-ins

• zigbee2mqtt - ZigBee gateway that exposes ZigBee certified devices (Philis Hue, Xiaomi Aqara, ...) via mqtt. Commonly used for home automation. list of supported devices

• MQTT.Cool - A web gateway that optimizes any MQTT broker when sending real-time data to web clients with automatic throttling.

• Eclipse Paho - provides an Eclipse view which can interact with a broker for testing.

• mqtt-watchdir - recursively watch a directory for modifications and publish file content to an MQTT broker.

• mqttfs - mqttfs allows you to mount a directory as effectively a link to an MQTT topic hierarchy on an MQTT server.