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.
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.
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-_`.
When encountering just the `<host>` without the `'<group-id>`, clients can choose to connect to the group with id `_`, which is a special top-level group dedicated to relay-local discussions.
Group identifiers in most cases should be random or pseudo-random, as that mitigates message replay confusiong and ensures they can be migrated or forked to other relays easily without risking conflicting with other groups using the same id in these new relays. This isn't a hard rule, as, for example, in `unmanaged` and/or ephemeral relays groups might not want to migrate ever, so they might not care about this. Notably, the `_` relay-local group isn't expected to be migrated ever.
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.
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.
This is the basic unit of a "microblog" reply note sent to a group. It's the same as `kind:11`, except for the fact that it must be used whenever it's in reply to some other note (either in reply to a `kind:11` or a `kind:12`). `kind:12` events SHOULD use NIP-10 markers, leaving an empty relay url:
*`["e", "<kind-11-root-id>", "", "root"]`
*`["e", "<kind-12-event-id>", "", "reply"]`
- *chat message* (`kind:9`)
This is the basic unit of a _chat message_ sent to a group.
Similar to `kind:12`, this is the basic unit of a chat message sent to a group. This is intended for in-chat threads that may be hidden by default. Not all in-chat replies MUST use `kind:10`, only when the intention is to create a hidden thread that isn't part of the normal flow of the chat (although clients are free to display those by default too).
`kind:10` SHOULD use NIP-10 markers, just like `kind:12`.
Groups may also accept other events, like long-form articles, calendar, livestream, 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 my user to manage their situation in a group, they also require the `h` tag.
Any user can send one of these events to the relay in order to be automatically or manually added to the group. If the group is `open` the relay will automatically issue a `kind:9000` in response adding this user. Otherwise group admins may choose to query for these requests and act upon them.
The optional `claim` tag may be used by the relay to preauthorize acceptances in `closed` groups, together with the `kind:9009``create-invite` moderation event.
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.
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.
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. The relay may discard the event after taking action or keep it as a moderation log.
| 9006 | `edit-group-status` | `public` or `private`, `open` or `closed` |
| 9007 | `create-group` | |
| 9008 | `delete-group` | |
| 9009 | `create-invite` | `code`, `uses` (how many times it can be used) |
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 are expected to 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).
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.
`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)
Similar to the group metadata, this event is supposed to be generated by relays that host the group.
Each admin gets a label that is only used for display purposes, and a list of permissions it has are listed afterwards. These permissions can inform client building UI, but ultimately are evaluated by the relay in order to become effective.
The list of capabilities, as defined by this NIP, for now, is the following:
It's a list of pubkeys that are members of the group. Relays might choose to not to publish this information or to restrict what pubkeys can fetch it.
Clients should not assume this will always be present or that it will contain a full list of members, as relays may opt to not publish it or publish a shortened version.
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](51.md) that allows clients to store the list of groups a user wants to remember being in.
To prevent event leakage, replay and confusion, when using `unmanaged` relays, clients should include the [NIP-70](70.md) `-` tag, as just the `previous` tag won't be checked by other `unmanaged` relays.
