Kind 10004: Communities

Overview

Communities events (kind 10004) allow users to maintain a list of Nostr communities they belong to or follow. This standard replaceable event kind serves as a user's record of community membership, making it easier to discover and organize participation in NIP-72 communities. By publishing this list, users can share which communities they're active in and help others discover interesting communities.

Specification

Property	Value
Kind Number	10004
Event Range	Replaceable
Defined in	NIP-51

Content Format

The content field can contain encrypted private community memberships using NIP-04 encryption. The encrypted content follows the same structure as the public tags but is only visible to the creator. This allows users to have both public community memberships (in tags) and private ones (encrypted in content).

Schema

For encrypted private communities:

"content": "<NIP-04 encrypted JSON array of tags>"

The encrypted content, when decrypted, would reveal a JSON array of tags:

[
  ["a", "34550:<pubkey>:<identifier>", "<relay-url>"]
]

Tags

Tag Name	Description	Format	Required
a	Community definition reference	["a", "34550:<pubkey>:<identifier>", "<relay-url>"]	Yes

Client Behavior

Clients should:

1. Display the user's community memberships in their profile or a dedicated section
2. Provide functionality to join (add) or leave (remove) communities
3. Use this list to filter and organize content from communities the user belongs to
4. Handle both public (in tags) and private (encrypted in content) community memberships
5. When displaying the communities list:
   • Fetch full community definitions from the provided relay hints
   • Show community names, descriptions, and other metadata
   • Provide quick navigation to community content
6. Include the community membership in relevant UI elements (e.g., filters, navigation)
7. When processing encrypted memberships, decrypt using NIP-04 and the user's keys
8. Maintain the chronological order of communities, with newest additions at the end

Relay Behavior

Relays should:

1. Handle kind 10004 events as normal replaceable events
2. Store these events to allow clients to retrieve the user's community memberships
3. Not attempt to interpret or enforce community membership (this is client-side functionality)

Use Cases

• Maintaining a list of communities a user is active in
• Discovering new communities through friends' memberships
• Organizing content by community affiliation
• Creating personalized community feeds
• Managing community participation
• Supporting community discovery and growth
• Building community directories based on member lists

Example

{
  "id": "c84a3da259b7b588c58284d6b0aa2f48e2a28c3c690b7b3cb5f6534ea1b7d358",
  "pubkey": "854043ae8f1f97430ca8c1f1a090bdde6488bd5115c7a45307a2a212750ae4cb",
  "created_at": 1699597889,
  "kind": 10004,
  "tags": [
    ["a", "34550:9be0be0e64d38a29a9cec9a5c8ef5d873c2bfa5362a4b558da5ff69bc3cbb81e:photography", "wss://relay.nostr.example.com"],
    ["a", "34550:7fa56f5d6962ab1e3cd424e758c3002b8665f7b0d8f2f2e67d2e6a7d15ce0d36:nostr-dev", "wss://relay.damus.io"],
    ["a", "34550:35ac9d0831cf9c08a85b46b96c56fb8ec097f4da780c57bec432c8449641a232:bitcoin", "wss://purplepag.es"]
  ],
  "content": "TJob1dQrf2ndsmdbeGU+05HT5GMnBSx3fx8QdDY/g3NvCa7klfzgaQCmRZuo1d3WQjHDOjzSY1+MgTK5WjewFFumCcOZniWtOMSga==?iv=S3rFeFr1gsYqmQA7bNnNTQ==",
  "sig": "a9a4e2192eede77e6c9d24ddfab95ba3ff7c03fbd07ad011fff245abea431fb4d3787c2d04aad001cb039cb8de91d83ce30e9a94f82ac3c5a2372aa1294a96bd"
}

References

• NIP-51: Lists
• NIP-72: Communities
• NIP-04: Encrypted Direct Messages

Related Kinds

• Kind 34550: Community Definition - Defines a community structure
• Kind 4550: Community Post Approval - Approvals for posts in communities
• Kind 1: Short Text Note - Notes often shared within communities
• Kind 30000: Follow Sets - For following users (vs. communities)

Notes

• Communities are one of several standard list types defined in NIP-51
• Users can only have one community list (since it's a replaceable event)
• The community definitions referenced should be kind 34550 events as defined in NIP-72
• This kind replaces the deprecated parameterized replaceable event with kind 30001 and d tag "communities"
• Community membership privacy can be managed by choosing whether to use public tags or encrypted content
• For maximum privacy, sensitive community memberships should be stored in the encrypted content field
• Relay hints in the a tags are recommended to help clients locate the community definitions