Support

Getting help with MQTT Explorer

Frequently Asked Questions

I can't connect to an external MQTT broker.

Check the broker host and port (default 1883 for plain MQTT, 8883 for MQTT over TLS). Ensure your Mac can reach the host — try ping broker.hivemq.com from Terminal. Verify any username/password and that the broker accepts connections from your network. For TLS brokers, confirm the port is 8883 and the correct CA certificate is selected.

The built-in broker won't start.

The default port 1883 may already be in use — often by a locally installed mosquitto. Either stop the other broker or change the built-in broker port in settings (e.g. 1884). Re-click Start Broker. The status indicator turns green when the broker is running.

How do I publish and subscribe to topics?

Connect to a broker (the built-in one or an external host). In the Publish panel, enter a topic (e.g. sensors/temperature), type a payload, pick a QoS, and hit Publish. In the Subscribe panel, enter a topic filter — wildcards + (single level) and # (multi level) are supported. Messages appear in the topic tree and message history in real time.

What QoS level should I use?

QoS 0 (at most once) is fine for high-frequency sensor readings where a missed message is quickly replaced. QoS 1 (at least once) for commands and events that must arrive — duplicates are possible. QoS 2 (exactly once) for billing or metering data where duplicates have a cost.

Does it support MQTT over WebSocket?

Yes. Connect with the ws:// or wss:// scheme on the broker's WebSocket port (commonly 8000 / 8883). Useful for testing browser- and Home Assistant-based clients that speak MQTT over WebSocket.

My license key doesn't work.

Enter the full key including dashes (format: VOLTRUS-MQTT-XXXX-XXXX-XXXX). An internet connection is required during first activation so the app can validate the key once. After activation, the app works offline. If it still fails, contact support below.

I bought from the Mac App Store. Do I need a license key?

No. The Mac App Store version is automatically licensed through your Apple ID. No license key needed. The paywall only appears in the direct-download (DMG) version.

I bought via Polar.sh but want to switch to the Mac App Store.

Purchases through Polar.sh and the Mac App Store are separate. We cannot transfer purchases between platforms. Both versions are identical in features.

The app crashes or freezes.

Make sure you're running macOS 13 (Ventura) or later. If the app freezes while publishing or subscribing, try disconnecting and reconnecting to the broker. If the issue persists, contact support with your macOS version, the app version, and what you were doing when it happened.

Contact Support

Email

For bug reports, feature requests, license issues, or general questions.

support@voltrus.id

Please include:

  • MQTT Explorer version (find in app → Info)
  • macOS version
  • Mac model (Intel or Apple Silicon)
  • Steps to reproduce the issue

Response Time

We aim to respond within 24 hours on business days. Complex issues may take longer. License-related questions are typically answered within a few hours.

Refund Policy

Mac App Store purchases: Refunds are handled by Apple through your App Store account settings.

Polar.sh purchases: Contact us at the email above within 30 days of purchase for a full refund. No questions asked.