A free, open-source MQTT.fx alternative

MQTT.fx is a polished, professional MQTT client with a long history. If you'd prefer a free, open-source option for connecting to brokers, inspecting topics, and publishing messages, MQTT Viewer is a great fit — on macOS, Windows, and Linux.

About MQTT.fx

MQTT.fx has been a familiar name in the MQTT world for years. The current version, MQTT.fx 5.x from Softblade, is a mature, professional desktop client with a Topic Explorer, message history, Sparkplug tooling, and commercial support — a product offered under paid licenses. It's worth noting there are really two tools with this name: the original, free MQTT.fx 1.x and today's commercial 5.x. A lot of people searching for a "free MQTT.fx" are looking for the spirit of that original tool.

Why people choose MQTT Viewer

MQTT Viewer takes a different approach: it's free and open-source, and aims to be the fastest way to see and debug what's happening on a broker. You get:

  • Free and open-source under GPL-3.0 — no license to buy, no account.
  • A live topic tree plus an interactive timeline and message comparison.
  • Up to 10 simultaneous broker connections.
  • Full MQTT v3.1.1 and v5 over TCP, TLS/SSL, mutual TLS, and WebSocket.
  • Sparkplug B, Base64, and Hex decoding built in.
  • Publish and re-publish from a searchable history.
  • A fast, native app for macOS, Windows, and Linux.

If you want a mature commercial tool with vendor support, MQTT.fx is a solid choice. If a free, open-source desktop client covers what you need, MQTT Viewer is ready in seconds.

Frequently asked questions

Is MQTT Viewer a free alternative to MQTT.fx?

Yes. MQTT Viewer is free and open-source under the GPL-3.0 license, with no license to buy and no account to create. It connects, subscribes, publishes, and decodes payloads — the everyday jobs you'd reach for an MQTT client to do.

What's the difference between the old and new MQTT.fx?

There are two products with the name: the original MQTT.fx 1.x, which was free, and the current MQTT.fx 5.x from Softblade, which is a commercial product with paid licenses. If you're looking for a free, open-source option, MQTT Viewer is a good fit.

Does MQTT Viewer support MQTT 5, TLS, and Sparkplug?

Yes. MQTT Viewer supports full MQTT v3.1.1 and v5, connections over TCP, TLS/SSL, mutual TLS, and WebSocket, and decoding for Sparkplug B, Base64, and Hex payloads.

Which platforms does MQTT Viewer run on?

MQTT Viewer is a native desktop app for macOS (Apple Silicon and Intel), Windows, and Linux (x86_64 and ARM64).

See how MQTT Viewer compares across the field in the best MQTT clients overview, or download MQTT Viewer for your platform.

MQTT Viewer is free, open-source, and runs on macOS, Windows & Linux.

Download MQTT Viewer