Kind 43: Channel Hide Message

Overview

Kind 43 events are used in the public chat system (NIP-28) to hide specific messages in a channel. This event type allows users to indicate they no longer want to see a particular message, providing client-side moderation capabilities without imposing requirements on relays. When a user creates a kind 43 event, clients should hide the referenced message when displaying the channel to that user.

Specification

Property	Value
Kind Number	43
Event Range	Regular
Defined in	NIP-28

Content Format

The content field is optional and may include metadata about the hide action, such as the reason for hiding the message. It should be a JSON string if provided.

Schema

"content": "{\"reason\": \"Inappropriate content\"}"

Tags

Tag Name	Description	Format	Required
e	Referenced message to hide	["e", "<message-event-id>"]	Yes

Client Behavior

Clients should:

1. Hide any kind 42 (channel message) events from display if the current user has created a kind 43 event referencing that message's ID
2. Allow users to easily create kind 43 events when they want to hide specific messages
3. Optionally support providing a reason when hiding a message
4. Optionally implement collective moderation by hiding messages that multiple users have hidden for certain reasons

Relay Behavior

Relays are not required to perform any special handling for kind 43 events. They should:

1. Store and serve these events like any other regular event
2. Not be expected to filter messages based on these events, as the filtering is handled client-side

Use Cases

• Personal content filtering in public chat channels
• Hiding spam, offensive content, or unwanted messages
• Creating safe, moderated environments without requiring relay-side moderation
• Collective moderation through aggregating user hide actions
• Building client-specific moderation policies based on user preferences

Example

{
  "id": "4376c65d2f232afbe9b882a35baa4f6fe8667c4e684749af565f981833ed6a65",
  "pubkey": "79dff8f82963424e0bb02708a22e44b4980893e3a4be0fa3cb60a43b946764e3",
  "created_at": 1671217411,
  "kind": 43,
  "tags": [
    ["e", "fe964e758903fc8186283d82b5f7029f0478d9daf9ea9a9ee8f7d620c4c99e98"]
  ],
  "content": "{\"reason\": \"Spam message\"}",
  "sig": "908a15e46fb4d8675bab026fc230a0e3542bfade63da02d542fb78b2a8513fcd0092619a2c8c1221e581946e0191f2af505dfdf8657a414dbca329186f009262"
}

Example with no reason provided:

{
  "id": "fe8b1c9a37218cf5ce604a8dce596c9c3ae0c650df2336f3c60c78e61a7b2031",
  "pubkey": "f7234bd4c1394dda46d09f35bd384dd30cc552ad5541990f98844fb06676e9ca",
  "created_at": 1671217500,
  "kind": 43,
  "tags": [
    ["e", "a1a2a3a4b1b2b3b4c1c2c3c4d1d2d3d4e1e2e3e4f1f2f3f4aaabbbcccddd"]
  ],
  "content": "",
  "sig": "a76f39224cebd44cf04eeebe01d5ab2e8f7a3e5e56c83cadd252e7bc5e2e34fd7ad7148cf7a2c7620d9490ccf2e1bac521995725f2e1f543159b8eb98bfdd405"
}

References

• NIP-28: Public Chat
• NIP-10: Text Notes and Threads (for channel message reply structure)

Related Kinds

• Kind 40: Channel Creation - Create a public chat channel
• Kind 41: Channel Metadata - Update channel information
• Kind 42: Channel Message - Send a message to a channel
• Kind 44: Channel Mute User - Hide all messages from a specific user

Notes

• The hide action is personal to the user who created the kind 43 event - it doesn't delete or hide the message for other users by default
• Clients may choose to implement collective moderation by aggregating hide events from multiple users
• For instance, if multiple users hide a message citing the same reason (e.g., "inappropriate content"), a client may choose to hide that message for all users
• This approach provides flexible, client-centric moderation without requiring changes to relay behavior
• The content field is optional but can be useful for categorizing reasons for moderation and implementing sophisticated filtering policies