NIP-9

NIP-09 provides a standard for deleting events in Nostr, specifying the behavior of relays and clients when handling deletion events, and outlining the conditions under which events should be hidden.

NIP-09 introduces a method for event deletion in Nostr. A special event with kind 5, meaning "deletion," is defined as having a list of one or more "e" tags, each referencing an event the author requests to be deleted. The event's content field may contain a text note describing the reason for the deletion.

Relays should delete or stop publishing any referenced events that have an identical pubkey as the deletion request. Clients should hide or otherwise indicate a deletion status for referenced events. Relays should continue to publish/share the deletion events indefinitely, as clients may already have the event that's intended to be deleted. Clients should broadcast deletion events to other relays which don't have it.

Client Usage:

1. Clients may choose to fully hide any events referenced by valid deletion events or show the event along with an icon or other indication that the author has "disowned" the event.

2. The content field may be used to replace the deleted events' content with the deletion reason.

3. Clients must validate that each event pubkey referenced in the "e" tag of the deletion request is identical to the deletion request pubkey before hiding or deleting any event.

Relay Usage:

1. Relays may validate that a deletion event only references events with the same pubkey as the deletion itself, but this is not required since relays may not have knowledge of all referenced events.

2. Deleting a deletion has no effect, and clients and relays are not obliged to support "undelete" functionality.