Public MQTT sandbox

Free public MQTT broker

Testing only. Never send secrets or production data.

This shared endpoint is for client tests and learning. It has no SLA, and credentials may rotate without notice.

Explore managed MQTT plans

Connection parameters

Host: public.runmqtt.com
TCP: 1883
TLSRecommended: 8883
WSS: wss://public.runmqtt.com/mqtt
Username: ajbkvbp/demo
Password: OCDWjjOSlSexcWRG
Client ID: runmqtt-test-<unique-id>

Client connection example

Use the current parameters above with unique client IDs and synthetic payloads.

Mosquitto CLI over TLS

# Load the current credentials shown on this page
export MQTT_USERNAME="ajbkvbp/demo"
export MQTT_PASSWORD="OCDWjjOSlSexcWRG"

# Subscribe
mosquitto_sub \
  -h public.runmqtt.com -p 8883 \
  -u "$MQTT_USERNAME" -P "$MQTT_PASSWORD" \
  -i "runmqtt-sub-$(date +%s)" \
  -t "sandbox/$USER/telemetry" -q 1

# Publish from another terminal
mosquitto_pub \
  -h public.runmqtt.com -p 8883 \
  -u "$MQTT_USERNAME" -P "$MQTT_PASSWORD" \
  -i "runmqtt-pub-$(date +%s)" \
  -t "sandbox/$USER/telemetry" -q 1 \
  -m '{"temperature":22.4,"unit":"C"}'

Browser connection test

Connect only to the RunMQTT public sandbox, subscribe to an automatically generated topic, and send one fixed synthetic message.

Disconnected

Shared testing only. Other users may observe messages. Never send secrets or production data.

Fixed WSS endpoint: wss://public.runmqtt.com/mqtt
Generated Client ID: Preparing…
Generated test topic: Preparing…
Synthetic payload: {"source":"runmqtt-browser-test","value":42}

Recent messages

Current tab · last 5

Connect, subscribe, then publish. A successful QoS 1 loopback appears here.

Usage limits

Testing and learning only

Do not use this endpoint for production devices or customer workloads.

Shared capacity, no SLA

Capacity is shared. Connections, credentials, and retained state may reset without notice.

Never send sensitive data

Other users may observe topic names and payloads. Publish synthetic data only.

When to upgrade

Use the sandbox to learn; use a managed cloud broker to operate

Broker capability
Broker capability	Public sandbox	Managed broker
Identity	Shared, rotating credentials	Scoped device credentials
Topic access	Shared namespace for disposable tests	Reusable publish and subscribe policies
Operations	Best effort with no lifecycle guarantees	Owned runtime, health, and billing state
Data	Synthetic payloads only	Private application workloads

Move when clients require a stable endpoint and credentials.

Move before using customer, device, or operational data.

Move when devices need different publish and subscribe rights.

Move when a demo becomes a repeatable integration or service.

Public MQTT broker FAQ

Can I send production traffic through the public broker?

No. The endpoint is shared, best effort, and may reset sessions or rotate access details. Use it for client validation, workshops, and short-lived demos only.

Should I use port 1883 or 8883?

Prefer 8883 with certificate validation. Port 1883 is useful only for isolated troubleshooting because payloads and credentials are not encrypted in transit.

Why can shared credentials change?

Rotation limits abuse and clears stale workshop access. Keep credentials in environment variables and check this page before a scheduled test.

Why does my client disconnect as soon as another client connects?

MQTT brokers allow one active session per client ID. Generate a unique client ID for every browser tab, process, device, and workshop participant.

Take the next step

Learn the protocol, harden the connection, then choose the operating model that fits your workload.