Part of: Field tools

MQTT broker and client.
Native on Mac. No Terminal.

Start a local MQTT broker with one click, then publish, subscribe and watch topics from Home Assistant, ESP32 or Arduino devices. No Electron, no Homebrew, no mosquitto config files.

Download for Mac (free) Buy Pro · $29.99 See what it does
Free
Pro $29.99
Broker
Built in
MQTT 3.1.1
QoS 0 / 1 / 2
macOS
Apple Silicon and Intel
MQTT Explorer screenshot: a table of topics with their latest payload, message count and retain flag.
A table of topics with their latest payload, message count and retain flag.
MQTT Explorer screenshot: topics folded into a tree with the latest payload on each leaf.
Topics folded into a tree with the latest payload on each leaf.
MQTT Explorer screenshot: payloads shown as formatted JSON alongside the subscription and publish panel.
Payloads shown as formatted JSON alongside the subscription and publish panel.

Demo video

Watch the demo

Subscribe with wildcards, explore the topic tree, read payloads as JSON, Hex or Base64, and run a local broker. A native Mac app.

Chapters

The Problem

A local MQTT broker on a Mac means Terminal.

Mosquitto needs Homebrew and a config file. MQTTX and the open-source MQTT Explorer are Electron apps. Node-RED is a whole flow runtime. You just want to see what your ESP32 is publishing.

01

No GUI Broker

Running a local broker usually means installing mosquitto via Homebrew and configuring it in Terminal. There is nothing to look at when a client fails to connect.

02

Electron Clients

MQTTX and the open-source MQTT Explorer are built on Electron, which bundles a full Chromium runtime for a tool you open for a few minutes. Neither runs a broker.

03

CLI-Only Broker

Install Homebrew, brew install mosquitto, edit the config file, start the daemon. Then you still have no view of connected clients or messages.

04

Node-RED Overkill

Node-RED can do MQTT, but it is a full flow-based programming environment on a Node.js runtime. Heavy for checking one topic.

Features

MQTT broker + client. One native app.

01

Built-In Broker

Start a local MQTT broker with one click. See its status and the topics flowing through it. Configure port, username/password users and TLS from the interface, and optionally open a WebSocket listener for browser clients.

02

Publish & Subscribe

Connect to any broker, local or remote. Publish messages to any topic. Subscribe with wildcards (# and +). QoS 0, 1, and 2 support.

03

Topic Tree Browser

Visual topic hierarchy shows all active topics in a tree view. Expand branches to see message payloads. Real-time updates as messages arrive.

04

Recent Messages

Recent messages are listed with topic, timestamp, retain flag and payload. JSON payloads are pretty-printed for reading.

05

MQTT 3.1.1

MQTT 3.1.1 with QoS 0, 1 and 2, retained messages, and Last Will and Testament on the client connection. New to QoS? Read MQTT QoS levels explained.

06

TLS/SSL

Encrypted connections with TLS/SSL: public CAs from the system trust store, a pinned CA for private or self-signed brokers, and client certificates for mutual TLS.

Screenshots

See it in action

MQTT Explorer screenshot: the message history with topic, QoS, time and payload for each message.
The message history with topic, QoS, time and payload for each message.
MQTT Explorer screenshot: a local broker started on the Mac, with topics arriving from connected devices.
A local broker started on the Mac, with topics arriving from connected devices.

Compare

How it compares to existing MQTT tools

Factor
MacTools MQTT Explorer
MQTTX (Electron)
Mosquitto CLI
Price
Free, Pro $29.99 one-time
Free
Free
Native macOS
Yes: Apple Silicon
Electron
N/A (CLI)
Built-in Broker
Yes: GUI
No
Yes: CLI only
Topic Tree Browser
Yes
Yes
No
MQTT 5.0
No (3.1.1 only)
Yes
Yes
Installation
One app, no extras
DMG download
Homebrew required

Part of: Field tools · Debug one device from your laptop: protocol apps, terminal database browsers, utilities.

How MacTools MQTT Explorer differs from…

  • Voltrus Broker

    The broker built into MQTT Explorer is a local one for testing on your machine. Voltrus Broker is a dedicated hosted broker your device fleet connects to around the clock.

  • RustRED

    RustRED runs flows that act on MQTT messages unattended. MQTT Explorer is the window you use to watch and publish those messages by hand.

  • MacTools suite

    Working with more than one protocol? MacTools has one native app per protocol, each sold on its own: 4 paid apps from $14.99 one-time, and free downloads with an optional one-time Pro licence.

Next step

Not sure? See which one you need →

FAQ

Common questions

Yes. The app includes a built-in MQTT broker you can start and stop from the GUI. No mosquitto, no Homebrew, no Docker. Just click Start Broker and your local MQTT server is running. The built-in broker is part of Pro.
Yes. Connect to any MQTT 3.1.1 broker by host and port, including your own self-hosted broker or a cloud broker that accepts 3.1.1. Supports MQTT over TLS/SSL for encrypted connections.
Yes. Use it to debug MQTT topics from your Home Assistant setup. Monitor sensor data, test automations, publish test messages to verify your smart home configuration.
MQTT 3.1.1, for both the client and the built-in broker. QoS levels 0, 1, and 2. Retained messages, Last Will and Testament, and topic wildcards (# and +). MQTT 5.0 is not supported.
No. The app is a free download. Pro is an optional one-time licence key for $29.99, bought through the Voltrus Console. There is no subscription.

Get it free

A local broker and a client. One native app.

MQTT Explorer is a free download for Mac. The DMG is signed and notarized by Apple, so it opens normally. An optional Pro licence key, $29.99 one-time, unlocks the Pro features below. The source is on GitHub under GPL-3.0.

Download for Mac (free) Buy Pro · $29.99 Source on GitHub Contact support

Optional Pro, $29.99 one-time licence key

  • Embedded local broker (TCP, WebSocket, TLS, username and password)
  • Several client connections at once and unlimited saved profiles
  • Custom CA, client certificates (mTLS) and Last Will
  • Sparkplug B decoding and protobuf decoding from your own .proto schema
  • Charts of numeric topic values
  • Message history CSV export and bulk-clear of retained messages

Pro is a one-time purchase on the Voltrus Console. Your key arrives by email and in your console account. No subscription.

From one device to the whole line

Need 24/7 monitoring?

MQTT Explorer is built for commissioning and debugging. For round-the-clock monitoring use Voltrus OEE (hosted, live availability and downtime per machine) or Voltrus SCADA (dashboards, alarms and history on your own hardware).

Voltrus OEE → Voltrus SCADA →

Get new tools, releases and protocol guides by email. A few emails a month, unsubscribe anytime.

You're subscribed. Thanks!

Also from MacTools

The full MacTools suite

Modbus Poll
Modbus TCP + RTU master and slave simulator. Read/write registers and coils.
Serial Terminal
RS232/RS485 serial terminal with a hex traffic view and ms timestamps.
MQTT Explorer
MQTT broker and client. Publish, subscribe and browse the topic tree. You're here.
NATS Explorer
NATS client with an embedded server, JetStream, KV and Object store.
S7 Explorer
Read and write Siemens S7-300/400/1200/1500 data blocks and memory areas.
EtherNet/IP Explorer
CIP device browser: tags, attributes, implicit and explicit messaging.
OPC-UA Explorer
OPC-UA client: browse namespaces, subscribe to nodes, manage certificates.
BACnet Explorer
BACnet/IP device discovery, object browser, property read/write.
DNP3 Explorer
DNP3 master and outstation simulator. Class polling and event scanning.
BLE Inspector
Scan BLE devices, browse GATT services, read, write and notify.
CNC Explorer
MTConnect and FANUC FOCAS client with an agent and a CNC simulator.
SECS/GEM Explorer
SECS/GEM host and equipment simulator over HSMS, with SML and event reports.
CAN Explorer
CAN and CAN FD monitor with DBC decoding, J1939 and CANopen labels, and a bus simulator.
PasteHere
Self-hosted pastebin that runs on your own Cloudflare account.