MQTT
An application messaging protocol with brokered routing, topics, delivery levels, retained messages, session state, and device-friendly clients.
Best for many-to-many IoT events, telemetry, state, and commands.
Protocol comparison
MQTT vs WebSocket: messaging protocol or communication channel?
MQTT defines publish-subscribe topics, QoS, sessions, retained state, and broker behavior. WebSocket creates a persistent full-duplex channel. They can compete in simple real-time apps, but MQTT can also run over WebSocket.
Separate transport from messaging semantics
WebSocket solves how bytes move over a persistent connection. MQTT also defines what the messaging system does with them.
WebSocket
A persistent bidirectional transport between a client and server. Message meaning, routing, authorization, replay, and acknowledgments belong to the application.
Best for custom browser-to-server real-time experiences.
| Capability | MQTT | WebSocket |
|---|---|---|
| Primary role | Application messaging protocol | Persistent full-duplex communication channel |
| Topology | Many publishers and subscribers coordinated by a broker | One client connection to one server endpoint |
| Routing | Built-in hierarchical topics and wildcard subscriptions | Application-defined events, rooms, channels, or handlers |
| Delivery behavior | QoS 0, 1, and 2 plus retained messages and session queues | Ordered frames on the connection; application adds acknowledgment and recovery |
| Browser support | Uses MQTT over WebSocket in browsers | Native browser API over ws or wss |
| Access control | Client identity plus publish and subscribe topic policy | Application session and custom message authorization |
Choose the smallest complete model
Avoid rebuilding broker semantics inside a WebSocket handler when the product actually needs topics, fan-out, offline behavior, and device identity.
Choose MQTT
When devices and services exchange telemetry, state, and commands through topics with defined delivery and session behavior.
Choose WebSocket
When a browser and application server need a custom live channel and the product does not need general broker semantics.
Use MQTT over WebSocket
When browser clients should join the same topic and policy model as devices, typically over secure WSS on port 443.
MQTT over WebSocket in practice
The browser uses WebSocket as the transport while MQTT remains the application protocol and broker contract.
Expose a WSS endpoint
Use a trusted TLS certificate, a documented path, and proxy timeouts that support long-lived connections.
Keep browser identity scoped
Issue short-lived or user-scoped broker credentials rather than embedding a shared device secret in frontend code.
Reuse topic policy
Authorize browser publish and subscribe actions through the same explicit topic contract used by other clients.
MQTT vs WebSocket FAQ
Are MQTT and WebSocket the same type of protocol?
No. MQTT defines application-level messaging semantics. WebSocket provides a persistent bidirectional channel. MQTT can use WebSocket as one of its transports.
Can a browser connect directly to MQTT?
Browsers cannot open arbitrary raw TCP sockets, so browser MQTT clients normally connect through a broker's WebSocket or secure WebSocket listener.
Is WebSocket faster than MQTT?
A direct frame can have less protocol work, but useful systems must also implement routing, delivery, recovery, and authorization. Measure the complete application path rather than frame overhead alone.
Related protocol guides
Compare the data-platform boundary, then implement and secure the MQTT connection.