Kind 40: Channel Creation

Overview

Channel Creation events (kind 40) are used to create public chat channels in Nostr. These events establish the foundation for group conversations, defining the channel's initial parameters and serving as the reference point for all subsequent channel-related events.

Specification

Property	Value
Kind Number	40
Event Range	Regular
Defined in	NIP-28

Content Format

The content field contains a JSON string with the channel's metadata. This includes basic information about the channel such as name, description, picture URL, and recommended relays.

Schema

{
  "name": "Demo Channel",
  "about": "A test channel for discussing Nostr development",
  "picture": "https://example.com/channel-image.jpg",
  "relays": [
    "wss://relay.example.com",
    "wss://another-relay.example.org"
  ]
}

Tags

Tag Name	Description	Format	Required
t	Channel category/topic	["t", "technology"]	No
Other standard tags (e.g., r for references) may be used as needed

Client Behavior

Clients should:

1. Allow users to create channels by publishing kind 40 events
2. Parse the metadata in the content field to display channel information
3. Store the event ID of the channel creation event for future reference
4. Use the specified relays in the channel metadata to fetch and publish channel-related messages
5. Display channel information including name, description, and picture

Relay Behavior

Relays should:

1. Store these events like other regular events
2. Allow clients to query for channels using event IDs or tags

Use Cases

• Creating public discussion forums
• Establishing topic-based communities
• Setting up team communication channels
• Creating interest-based group chats
• Building public support or help channels

Example

{
  "id": "4376c65d2f232afbe9b882a35baa4f6fe8667c4e684749af565f981833ed6a65",
  "pubkey": "79dff8f82963424e0bb02708a22e44b4980893e3a4be0fa3cb60a43b946764e3",
  "created_at": 1671217411,
  "kind": 40,
  "tags": [
    ["t", "technology"],
    ["t", "programming"],
    ["t", "nostr"]
  ],
  "content": "{\"name\": \"Nostr Development\", \"about\": \"A channel for discussing Nostr protocol development and implementation\", \"picture\": \"https://example.com/nostr-dev.png\", \"relays\": [\"wss://relay.example.com\", \"wss://nostr.example.org\"]}",
  "sig": "908a15e46fb4d8675bab026fc230a0e3542bfade63da02d542fb78b2a8513fcd0092619a2c8c1221e581946e0191f2af505dfdf8657a414dbca329186f009262"
}

Channel Metadata

The JSON in the content field should include:

• name (required): The name of the channel
• about (recommended): Channel description/purpose
• picture (optional): URL to an image representing the channel
• relays (recommended): Array of relay URLs where channel messages should be published/fetched

Additional custom fields may be included for extended functionality.

Channel Ownership

The channel is considered to be "owned" by the creator (the pubkey that published the kind 40 event). This is important because:

1. Only the owner can update channel metadata via kind 41 events
2. Clients should validate that channel metadata updates come from the original creator
3. The owner may have additional privileges defined by client implementations

Channel Management

After creation, the channel can be managed using:

• Kind 41: Update channel metadata
• Kind 42: Post messages to the channel
• Kind 43: Hide specific messages
• Kind 44: Mute specific users

References

• NIP-28: Public Chat
• NIP-10: Event References - For reply threading

Related Kinds

• Kind 41: Channel Metadata - Update channel information
• Kind 42: Channel Message - Post messages in channels
• Kind 43: Channel Hide Message - Moderation tool to hide messages
• Kind 44: Channel Mute User - Moderation tool to mute users

Notes

• Channel creation establishes a unique identifier (the event ID) that will be referenced by all subsequent channel-related events
• The Nostr chat system is client-centric, meaning most moderation happens at the client level
• There's no guarantee that all clients will respect the same moderation decisions
• Multiple channels with the same name can exist; they are distinguished by their event IDs