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HiveMQ - Deny Wildcard Plugin

by HiveMQ Team
3 min read

We just released a new plugin: The Deny Root Wildcard Subscriptions Plugin for HiveMQ. With this plugin all subscriptions to the root wildcard topic (’#’) are denied by the broker and the client gets disconnected.

The Challenge With Root Wildcards

A subscribing client which subscribes the root wildcard will receive *every message which is ever published to a broker by any client. This means, the subscribing client has to handle an amount of messages which can be close to the message amount a broker has to handle. Such a subscriber can be an absolute bottleneck in many scenarios. In practice, it’s very hard to find a MQTT client library which can handle massive amounts of messages without slowing down something.

To protect yourself against this kind of subscribers, we developed this simple plugin. It’s super simple and because of this, it’s also a good starting point for your own plugin developments.


  1. Navigate to the HiveMQ plugin store and download the latest version of the “Deny Root Wildcard Subscriptions” plugin and click “Download”.

  2. Unzip the zip file and copy the jar file to the “<HIVEMQ_HOME>/plugins” directory

  3. Done. No configuration needed


The Deny Root Wildcard Subscriptions plugin is a great way to protect yourself against subscribers on the root topic. The source code is available on Github under a commercial-friendly Apache2 license.

The plugin SDK of HiveMQ is free and open source and it’s dead easy to implement your own plugins in the shortest time possible.

Which plugins would you like to see next? Contact us.

HiveMQ Team

The HiveMQ team loves writing about MQTT, Sparkplug, Industrial IoT, protocols, how to deploy our platform, and more. We focus on industries ranging from energy, to transportation and logistics, to automotive manufacturing. Our experts are here to help, contact us with any questions.

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