Kind 9: Chat Message

Overview

Chat Message events (kind 9) are used for general chat messaging in the Nostr ecosystem. Unlike the more structured public chat system defined in NIP-28 (kinds 40-44), kind 9 events are intended for simple, direct chat functionality.

Specification

Property	Value
Kind Number	9
Event Range	Regular
Defined in	NIP-C7

Content Format

The content field contains the message text. When replying to another message, it may include a NIP-21 nostr: URI reference to the message being replied to, followed by the reply text.

Schema

// Simple message
"content": "Hello world!"

// Reply (with embedded reference)
"content": "nostr:nevent1qs24jxa5mtk64upwsajlnzkukcucgj057thv3hzn43f0qe25cjkqppemhq4\nGood to hear from you!"

Tags

Tag Name	Description	Format	Required
q	Referenced message (for replies)	["q", "<event-id>", "<relay-url>", "<pubkey>"]	No (Yes for replies)
Additional tags may be added according to common conventions for targeting or context

Client Behavior

Clients should:

1. Display chat messages in a conversational interface
2. For replies, show threading or other visual indication of reply context
3. When creating a reply:
   • Include a q tag referencing the message being replied to
   • Optionally include the NIP-21 reference to the original message in the content

Relay Behavior

Relays should:

1. Store and deliver chat message events like other regular events
2. Properly handle queries that filter by the q tag for fetching replies

Use Cases

• Simple messaging between users
• Casual conversations
• Quick exchanges without the structure of public chat channels
• Thread-like discussions through replies

Example

// Simple chat message
{
  "id": "4376c65d2f232afbe9b882a35baa4f6fe8667c4e684749af565f981833ed6a65",
  "pubkey": "79dff8f82963424e0bb02708a22e44b4980893e3a4be0fa3cb60a43b946764e3",
  "created_at": 1671217411,
  "kind": 9,
  "tags": [],
  "content": "GM",
  "sig": "908a15e46fb4d8675bab026fc230a0e3542bfade63da02d542fb78b2a8513fcd0092619a2c8c1221e581946e0191f2af505dfdf8657a414dbca329186f009262"
}

// Reply to the above message
{
  "id": "5d83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36",
  "pubkey": "f7234bd4c1394dda46d09f35bd384dd30cc552ad5541990f98844fb06676e9ca",
  "created_at": 1671217500,
  "kind": 9,
  "tags": [
    ["q", "4376c65d2f232afbe9b882a35baa4f6fe8667c4e684749af565f981833ed6a65", "wss://relay.example.com", "79dff8f82963424e0bb02708a22e44b4980893e3a4be0fa3cb60a43b946764e3"]
  ],
  "content": "nostr:nevent1qs24jxa5mtk64upwsajlnzkukcucgj057thv3hzn43f0qe25cjkqppemhq4\nGM to you too!",
  "sig": "a76f39224cebd44cf04eeebe01d5ab2e8f7a3e5e56c83cadd252e7bc5e2e34fd7ad7148cf7a2c7620d9490ccf2e1bac521995725f2e1f543159b8eb98bfdd405"
}

References

• NIP-C7: Chats
• NIP-21: nostr: URI scheme

Related Kinds

• Kind 40-44: Public Chat - More structured public chat system
• Kind 14: Direct Message - Encrypted private messages

Notes

• The q tag follows the same conventions as the e tag in NIP-10, except that the marker parameter is not used.
• Chat messaging in Nostr is still evolving, with different approaches being used by different clients.
• This kind represents a simpler approach to chat than the more structured channel-based system in NIP-28.