MQTT Tester

Connect to an MQTT broker over WebSockets, subscribe to topics, publish messages, and inspect a live message log — all from your browser.

Browsers can only reach an MQTT broker over WebSockets (ws:// or wss://) — plain TCP-only brokers (port 1883/8883) are not reachable from here. Most public test brokers and self-hosted setups need an explicit WebSocket listener enabled, and public brokers may rate-limit or occasionally be unavailable.
Disconnected
Subscribe

No active subscriptions.

Publish

No messages yet. Connect, subscribe to a topic, and publish a message to see it here.

Connects to an MQTT broker using MQTT-over-WebSockets (via MQTT.js). Nothing is sent anywhere except to the broker you specify — this tool does not proxy or log your traffic. Payloads that aren't valid UTF-8 text are shown as hex.

MQTT Tester

Connect to an MQTT broker over WebSockets, subscribe to topics, publish messages, and inspect a live message log — all from your browser.

Common uses

  • Subscribe to a topic and watch live sensor messages
  • Publish a retained message to an MQTT broker
  • Test an IoT device topic hierarchy

Frequently asked questions

Can I use MQTT Tester to subscribe to a topic and watch live sensor messages?

Yes. MQTT Tester can subscribe to a topic and watch live sensor messages, directly in your browser.

Can I use MQTT Tester to publish a retained message to an MQTT broker?

Yes. MQTT Tester can publish a retained message to an MQTT broker, directly in your browser.

Can I use MQTT Tester to test an IoT device topic hierarchy?

Yes. MQTT Tester can test an IoT device topic hierarchy, directly in your browser.

Is my data uploaded to a server?

No. This tool runs entirely in your browser — your input is processed locally on your device and is never uploaded or stored on a server.