NATS and JetStream on your Mac.
Embedded server. No CLI.
NATS pub/sub, an embedded server, JetStream streams and consumers, Key-Value and Object stores, and protobuf payload decode in one native window. No Docker, no nats-server daemon, no Electron.
Demo video
Watch the demo
Run an embedded NATS server, watch live traffic on any subject, see JetStream streams, and browse KV buckets and object stores. A native Mac app.
Chapters
Features
A full NATS toolkit. One native window.
Pub/sub, an embedded server, JetStream, KV, Object store, schema-aware payload decode, and server monitoring, all in one native app.
Pub / Sub Client
Connect to any NATS server. Publish messages and subscribe with wildcard subjects (* and >). Full message header support, request/reply, and queue groups.
Embedded NATS Server
Start and stop a real NATS server from the GUI for local development and demos. No Docker container, no nats-server binary, no daemon to configure. Click Start and you have a broker.
JetStream Streams
Create, inspect, purge, and delete streams. Browse stored messages with sequence, subject, and timestamp. Export a stream's messages to CSV for offline analysis.
JetStream Consumers
Create durable and ephemeral consumers, fetch the next message, acknowledge, and watch pending counts, ack-pending, and redelivery metrics. Debug pull and push consumers without the CLI.
Key-Value Store
Manage KV buckets and keys: get, put, delete, and revision history. Live-watch a key or a whole bucket and see value changes as they happen.
Object Store
Browse Object store buckets. Upload files from disk, download objects back, put an inline payload, and list or delete entries. Large blobs chunked over JetStream, no extra service.
Protobuf Schema Registry
Import .proto files and bind subject patterns to a protobuf message. Messages on matching subjects decode into readable JSON automatically: you see fields, not hex.
Payload Viewer
Auto-detect JSON, protobuf, or raw bytes. Pretty-print JSON, render bound protobuf messages as fields, and fall back to a hex/string view for everything else.
Server Monitor ($SYS)
Subscribe to $SYS.> for live server stats, connections, accounts, and slow-consumer alerts. Pretty-printed JSON so the monitoring stream is actually readable.
Screenshots
See it in action
Compare
How it compares to the usual NATS workflow
Inspecting NATS today means the nats CLI plus nats-server in Docker, or a web playground. Here's how that stacks up against a native app.
Use Cases
Built for NATS developers on macOS.
Microservice messaging, event streams, edge IoT, and protobuf contract testing: inspect and debug it all without leaving your Mac.
Microservice Messaging
Subscribe to orders.* and payments.* across services. Watch the full message flow with headers and payloads, catch missing fields before they hit production.
JetStream Debugging
A consumer not acking? Inspect the stream, fetch the next message, and read pending and redelivery counts. Purge and replay without dropping into the CLI.
Local Development
Run the embedded server, point your apps at nats://localhost:4222, and develop against real JetStream, KV, and Object stores, no Docker Compose file to maintain.
Protobuf Contract Testing
Import your .proto, bind subject patterns, and check that every published message decodes cleanly. Spot schema drift between producer and consumer early.
Config & State Inspection
Browse a KV bucket of feature flags or shared config, watch a key for live changes, and read revision history to see what changed and when.
Edge IoT Messaging
Bridge device telemetry over NATS at the edge. Monitor $SYS.> for connection drops and slow consumers, and decode protobuf sensor payloads inline.
Part of: Field tools · Debug one device from your laptop: protocol apps, terminal database browsers, utilities.
How MacTools NATS Explorer differs from…
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MacTools MQTT Explorer
MQTT Explorer does the same job for MQTT: publish, subscribe and a local test broker.
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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.
FAQ
Common questions
nats-server binary, no CLI. Click Start and your local NATS (with JetStream) is running for development and demos.nats:// or wss://), with TLS and credential or JWT authentication. Works with Synadia Cloud, a self-hosted cluster, or the embedded local server..proto files, then bind a subject pattern (e.g. orders.*) to a protobuf message. Messages on matching subjects are decoded into readable JSON automatically instead of raw bytes, so you see fields, not hex. Protobuf decoding is part of Pro.nats-server daemon to configure. Install the app and you have a full NATS + JetStream environment.Get it free
A NATS client and server in one Mac app.
NATS 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.
Optional Pro, $29.99 one-time licence key
- JetStream stream and consumer create, delete and purge, stored message fetch
- KV store browser with live watch
- Object store browser with upload and download
- $SYS server monitor
- Protobuf schema decoding and message CSV export
- Unlimited saved connection profiles
Pro is a one-time purchase on the Voltrus Console. Your key arrives by email and in your console account. No subscription.
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From one device to the whole line
Need 24/7 monitoring?
NATS 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).
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