NIP-2

NIP-2 establishes contact lists and petnames for following, sharing, and discovering profiles, while providing a local naming system.

NIP-2 introduces the concept of contact lists and petnames within the NOSTR protocol. Contact lists are special events with a kind value of 3 and are composed of a list of "p" tags, each representing a followed or known profile. These lists can be used for contact list backup, profile discovery, context augmentation, relay sharing, and petname schemes. By sharing contact lists with relay URLs, clients can increase censorship resistance and discover new profiles, while the petname scheme allows for local naming conventions without requiring global human-readable names.

An example of a contact list event is shown below:

{
  "kind": 3,
  "tags": [
    ["p", "91cf9..4e5ca", "wss://alicerelay.com/", "alice"],
    ["p", "14aeb..8dad4", "wss://bobrelay.com/nostr", "bob"],
    ["p", "612ae..e610f", "ws://carolrelay.com/ws", "carol"]
  ],
  "content": "",
  ...other fields
}

Each contact list entry contains the profile's key, a relay URL, and a local name or petname. When a new contact list is published, it overwrites previous ones, requiring relays and clients to delete past contact lists upon receiving a new one.