NIP-29 - Relay-based Groups

Table of Contents

• Relay-based Groups
• Relay-generated events
• Group identifier
• The h tag
• Timeline references
• Late publication
• Group management
• Unmanaged groups
• Event definitions
  • Normal user-created events
  • User-related group management events
  • Group state -- or moderation
  • Group metadata events
• Implementation quirks
  • Checking your own membership in a group
  • Adding yourself to a group
  • Storing your list of groups
  • Using unmanaged relays

Relay-based Groups

draft optional

This NIP defines a standard for groups that are only writable by a closed set of users. They can be public for reading by external users or not.

Groups are identified by a random string of any length that serves as an id.

There is no way to create a group, what happens is just that relays (most likely when asked by users) will create rules around some specific ids so these ids can serve as an actual group, henceforth messages sent to that group will be subject to these rules.

Normally a group will originally belong to one specific relay, but the community may choose to move the group to other relays or even fork the group so it exists in different forms -- still using the same id -- across different relays.

Relay-generated events

Relays are supposed to generate the events that describe group metadata and group admins. These are addressable events signed by the relay keypair directly, with the group id as the d tag.

Group identifier

A group may be identified by a string in the format <host>'<group-id>. For example, a group with id abcdef hosted at the relay wss://groups.nostr.com would be identified by the string groups.nostr.com'abcdef.

Group identifiers must be strings restricted to the characters a-z0-9-_, and SHOULD be random in order to avoid name collisions.

When encountering just the <host> without the '<group-id>, clients MAY infer _ as the group id, which is a special top-level group dedicated to relay-local discussions.

The h tag

Events sent by users to groups (chat messages, text notes, moderation events etc) MUST have an h tag with the value set to the group id.

Timeline references

In order to not be used out of context, events sent to these groups may contain references to previous events seen from the same relay in the previous tag. The choice of which previous events to pick belongs to the clients. The references are to be made using the first 8 characters (4 bytes) of any event in the last 50 events seen by the user in the relay, excluding events by themselves. There can be any number of references (including zero), but it's recommended that clients include at least 3 and that relays enforce this.

This is a hack to prevent messages from being broadcasted to external relays that have forks of one group out of context. Relays are expected to reject any events that contain timeline references to events not found in their own database. Clients should also check these to keep relays honest about them.

Late publication

Relays should prevent late publication (messages published now with a timestamp from days or even hours ago) unless they are open to receive a group forked or moved from another relay.

Group management

Groups can have any number of users with elevated access. These users are identified by role labels which are arbitrarily defined by the relays (see also the description of kind:39003). What each role is capable of not defined in this NIP either, it's a relay policy that can vary. Roles can be assigned by other users (as long as they have the capability to add roles) by publishing a kind:9000 event with that user's pubkey in a p tag and the roles afterwards (even if the user is already a group member a kind:9000 can be issued and the user roles must just be updated).

The roles supported by the group as to having some special privilege assigned to them should be accessible on the event kind:39003, but the relay may also accept other role names, arbitrarily defined by clients, and just not do anything with them.

Users with any roles that have any privilege can be considered admins in a broad sense and be returned in the kind:39001 event for a group.

Unmanaged groups

Unmanaged groups are impromptu groups that can be used in any public relay unaware of NIP-29 specifics. They piggyback on relays' natural white/blacklists (or lack of) but aside from that are not actively managed and won't have any admins, group state or metadata events.

In unmanaged groups, everybody is considered to be a member.

Unmanaged groups can transition to managed groups, in that case the relay master key just has to publish moderation events setting the state of all groups and start enforcing the rules they choose to.

Event definitions

These are the events expected to be found in NIP-29 groups.

Normal user-created events

Groups may accept any event kind, including chats, threads, long-form articles, calendar, livestreams, market announcements and so on. These should be as defined in their respective NIPs, with the addition of the h tag.

User-related group management events

These are events that can be sent by users to manage their situation in a group, they also require the h tag.

• join request (kind:9021)

Any user can send a kind 9021 event to the relay in order to request admission to the group. Relays MUST reject the request if the user has not been added to the group. The accompanying error message SHOULD explain whether the rejection is final, if the request is pending review, or if some other special handling is relevant (e.g. if payment is required). If a user is already a member, the event MUST be rejected with duplicate: as the error message prefix.

{
  "kind": 9021,
  "content": "optional reason",
  "tags": [
    ["h", "<group-id>"],
    ["code", "<optional-invite-code>"]
  ]
}

The optional code tag may be used by the relay to preauthorize acceptances in closed groups, together with the kind:9009 create-invite moderation event.

• leave request (kind:9022)

Any user can send one of these events to the relay in order to be automatically removed from the group. The relay will automatically issue a kind:9001 in response removing this user.

{
  "kind": 9022,
  "content": "optional reason",
  "tags": [
    ["h", "<group-id>"]
  ]
}

Group state -- or moderation

These are events expected to be sent by the relay master key or by group admins -- and relays should reject them if they don't come from an authorized admin. They also require the h tag.

• moderation events (kinds:9000-9020) (optional)

Clients can send these events to a relay in order to accomplish a moderation action. Relays must check if the pubkey sending the event is capable of performing the given action based on its role and the relay's internal policy (see also the description of kind:39003).

{
  "kind": 90xx,
  "content": "optional reason",
  "tags": [
    ["h", "<group-id>"],
    ["previous", /*...*/]
  ]
}

Each moderation action uses a different kind and requires different arguments, which are given as tags. These are defined in the following table:

It's expected that the group state (of who is an allowed member or not, who is an admin and with which permission or not, what are the group name and picture etc) can be fully reconstructed from the canonical sequence of these events.

Group metadata events

These events contain the group id in a d tag instead of the h tag. They MUST be created by the relay master key only and a single instance of each (or none) should exist at all times for each group. They are merely informative but should reflect the latest group state (as it was changed by moderation events over time).

• group metadata (kind:39000) (optional)

This event defines the metadata for the group -- basically how clients should display it. It must be generated and signed by the relay in which is found. Relays shouldn't accept these events if they're signed by anyone else.

If the group is forked and hosted in multiple relays, there will be multiple versions of this event in each different relay and so on.

When this event is not found, clients may still connect to the group, but treat it as having a different status, unmanaged,

{
  "kind": 39000,
  "content": "",
  "tags": [
    ["d", "<group-id>"],
    ["name", "Pizza Lovers"],
    ["picture", "https://pizza.com/pizza.png"],
    ["about", "a group for people who love pizza"],
    ["public"], // or ["private"]
    ["open"] // or ["closed"]
  ]
  // other fields...
}

name, picture and about are basic metadata for the group for display purposes. public signals the group can be read by anyone, while private signals that only AUTHed users can read. open signals that anyone can request to join and the request will be automatically granted, while closed signals that members must be pre-approved or that requests to join will be manually handled.

• group admins (kind:39001) (optional)

Each admin is listed along with one or more roles. These roles SHOULD have a correspondence with the roles supported by the relay, as advertised by the kind:39003 event.

{
  "kind": 39001,
  "content": "list of admins for the pizza lovers group",
  "tags": [
    ["d", "<group-id>"],
    ["p", "<pubkey1-as-hex>", "ceo"],
    ["p", "<pubkey2-as-hex>", "secretary", "gardener"],
    // other pubkeys...
  ],
  // other fields...
}

• group members (kind:39002) (optional)

It's a list of pubkeys that are members of the group. Relays might choose to not to publish this information, to restrict what pubkeys can fetch it or to only display a subset of the members in it.

Clients should not assume this will always be present or that it will contain a full list of members.

{
  "kind": 39002,
  "content": "list of members for the pizza lovers group",
  "tags": [
    ["d", "<group-id>"],
    ["p", "<admin1>"],
    ["p", "<member-pubkey1>"],
    ["p", "<member-pubkey2>"],
    // other pubkeys...
  ],
  // other fields...
}

• group roles (kind:39003) (optional)

This is an event that MAY be published by the relay informing users and clients about what are the roles supported by this relay according to its internal logic.

For example, a relay may choose to support the roles "admin" and "moderator", in which the "admin" will be allowed to edit the group metadata, delete messages and remove users from the group, while the "moderator" can only delete messages (or the relay may choose to call these roles "ceo" and "secretary" instead, the exact role name is not relevant).

The process through which the relay decides what roles to support and how to handle moderation events internally based on them is specific to each relay and not specified here.

{
  "kind": 39003,
  "content": "list of roles supported by this group",
  "tags": [
    ["d", "<group-id>"],
    ["role", "<role-name>", "<optional-description>"],
    ["role", "<role-name>", "<optional-description>"],
    // other roles...
  ],
  // other fields...
}

Implementation quirks

Checking your own membership in a group

The latest of either kind:9000 or kind:9001 events present in a group should tell a user that they are currently members of the group or if they were removed. In case none of these exist the user is assumed to not be a member of the group -- unless the group is unmanaged, in which case the user is assumed to be a member.

Adding yourself to a group

When a group is open, anyone can send a kind:9021 event to it in order to be added, then expect a kind:9000 event to be emitted confirming that the user was added. The same happens with closed groups, except in that case a user may only send a kind:9021 if it has an invite code.

Storing your list of groups

A definition for kind:10009 was included in NIP-51 that allows clients to store the list of groups a user wants to remember being in.

Using unmanaged relays

To prevent event leakage, when using unmanaged relays, clients should include the NIP-70 - tag, as just the previous tag won't be checked by other unmanaged relays.

Groups MAY be named without relay support by adding a name to the corresponding tag in a user's kind 10009 group list.