NanoMQ

Eclipse Mosquitto

eclipse-mosquitto/mosquitto

Popular

Lightweight, ubiquitous open-source MQTT broker; the default choice for small deployments and gateways.

EMQX

emqx/emqx

Popular

Highly scalable Erlang MQTT 5 broker and platform with clustering, rule engine and data bridges.

MQTT.js

mqttjs/MQTT.js

Popular

The standard MQTT client for Node.js and browsers (over WebSockets), supporting MQTT 3.1.1 and 5.

Eclipse Paho

eclipse-paho/paho.mqtt.python

Popular

Family of MQTT client libraries for Python, C, Java and more; paho-mqtt is the default Python client.

HiveMQ CE

hivemq/hivemq-community-edition

Java-based open-source edition of the HiveMQ MQTT broker with an extension SDK; enterprise version available.

VerneMQ

vernemq/vernemq

Distributed, Erlang-based MQTT broker focused on clustering and high availability.

Zenoh

eclipse-zenoh/zenoh

Rising

Pub/sub/query protocol unifying data in motion and at rest from MCU to cloud; an official ROS 2 middleware.

NATS

nats-io/nats-server

Lightweight, high-performance messaging with JetStream persistence, KV and object store.

ejabberd

processone/ejabberd

Robust, Ubiquitous and Massively Scalable Messaging Platform (XMPP, MQTT, SIP Server)