How Meshtastic Channels Work

How Meshtastic Channels Work

Meshtastic uses a channel system for message segmentation and encryption. Each node can have up to 8 channels simultaneously, each with its own name and encryption key.

Channel Structure

• Up to 8 channels per node, indexed 0 through 7
• Channel 0 is the primary channel. Position updates and telemetry are broadcast on channel 0 by default.
• Each channel has:
  • A name (displayed in the app)
  • A pre-shared key (PSK) —- the encryption key for that channel
  • Optional uplink/downlink MQTT settings for internet bridging

The Default Public Channel

Out of the box, Meshtastic nodes are configured with:

• Channel name: LongFast
• PSK: AQ== (a well-known public key; all Meshtastic nodes know this key by default)

Any node using the default LongFast channel can communicate with any other node using the same channel —- the encryption provides no privacy since the key is public. This is intentional: it allows strangers to discover and communicate across the mesh.

Channel URL Scheme

Channels are shareable via URL or QR code. Example channel URL:

meshtastic.org/e/#CgUYAyIBAQ==

The hash after # is a base64-encoded channel configuration. To encode or decode channel configurations, use the tool at meshtastic.org/e/.

Sharing a channel URL (or its QR code) is the standard way to invite someone to a private channel —- they scan or paste the URL and their node is automatically configured with the correct name and PSK.

MQTT Uplink and Downlink

Each channel can be individually configured to bridge traffic to/from an MQTT broker:

meshtastic --ch-index 0 --ch-set uplink_enabled true
meshtastic --ch-index 0 --ch-set downlink_enabled true

When uplink is enabled on a channel, packets on that channel are published to the MQTT broker. Downlink delivers MQTT messages back to the mesh. This is the basis of Meshtastic internet bridging and long-distance message delivery via the MQTT network.

Admin Channel

A designated private admin channel allows remote configuration of any node that shares the admin channel’channel's PSK:

• Create a channel with a unique name (e.g., admin) and a strong, randomly generated PSK
• Configure it as the admin channel on all nodes you want to remotely manage
• From any node with the admin channel, you can send configuration commands to remote nodes over the mesh —- no physical access required

This is essential for maintaining remote or hard-to-reach infrastructure nodes.