MQTT vs HTTP for IoT Applications
Use MQTT when many small messages must flow between devices and services, especially over unreliable or constrained networks; use HTTP when a device makes occasional requests to a web API or when you need simple integration with existing web services. Many systems use both.
Comparison
| MQTT | HTTP | |
|---|---|---|
| Model | Publish/subscribe via a broker | Request/response between client and server |
| Connection | Long-lived, persistent | Typically short-lived per request (keep-alive possible) |
| Server push | Native: subscribers receive messages instantly | Needs polling, WebSockets or SSE |
| Overhead | Very small headers | Larger text headers |
| Delivery guarantees | QoS 0, 1 and 2 | Application-level retries |
| Offline awareness | Last Will, retained messages | None built in |
| Tooling | Brokers, MQTT clients | Universal: browsers, REST tools, CDNs |
Choose MQTT for
- Telemetry from many devices at frequent intervals.
- Commands that must reach a device quickly (relays, setpoints).
- Battery-powered nodes that cannot afford heavy request overhead.
Choose HTTP for
- Occasional uploads of a batch of readings.
- Calling third-party APIs (weather, SMS, webhooks).
- Firmware downloads and configuration endpoints.
Design tip: use both
A common pattern is MQTT between devices and a gateway or back end, and HTTP between the back end and web applications. A gateway such as a Raspberry Pi can translate between them. See MQTT explained for the protocol details and the MQTT and Node-RED course for hands-on practice.
References
- OASIS, MQTT Version 5.0: docs.oasis-open.org
- IETF RFC 9110, HTTP Semantics: rfc-editor.org
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