Nostr Tags

Tags are key components of Nostr events that provide additional context, metadata, and relationships between events. They are especially important for the discoverability and interconnectedness of the Nostr protocol.

Available Tag Definitions

The following tags have detailed definitions in this documentation:

Tag Name	Description	Defined in
a	References an addressable or replaceable event	NIP-01
alt	Provides human-readable summary for custom event kinds	NIP-31
d	Provides a unique identifier for addressable events	NIP-01
e	References another event	NIP-01
g	Provides geographic location using a geohash	NIP-52
h	Identifies a group in the relay-based groups system	NIP-29
i	References external identities and content identifiers	NIP-39, NIP-35, NIP-73
p	References a user's public key	NIP-01
q	References an event in a quote repost	NIP-18
r	References a URL or relay address	NIP-24, NIP-65
t	Hashtags for content categorization	NIP-24
-	Indicates a "protected" event that can only be published by its author	NIP-70
client	Identifies the client application that published an event	NIP-89
emoji	Defines a custom emoji for use in event content	NIP-30
imeta	Provides metadata about media URLs in event content	NIP-92
proxy	Links events to their original source from other protocols	NIP-48
zap	Specifies recipients for Lightning Network payments (zaps) on events	NIP-57

Tag Format

In Nostr events, tags are represented as arrays of strings within the tags array of an event. The first element of a tag array is always the tag name, followed by one or more values.

Example:

{
  "kinds": 1,
  "tags": [
    ["client", "MyNostrClient"],
    ["d", "article-identifier"],
    ["e", "5c83da77af1dec6d7289834998ad7aafbd9e2191396d75ec3cc27f5a77226f36", "", "reply"],
    ["p", "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245"],
    ["a", "30023:f7234bd4c1394dda46d09f35bd384dd30cc552ad5541990f98844fb06676e9ca:abcd"]
  ],
  // other fields...
}

Tag Categories

Tags in Nostr can serve several purposes:

1. Referencing other events (e.g., e tag for event references)
2. Referencing users (e.g., p tag for pubkey references)
3. Referencing addressable content (e.g., a tag for replaceable or addressable events)
4. Identifying content (e.g., d tag for uniquely identifying addressable events)
5. Providing metadata (e.g., client tag for identifying the publishing application)
6. Defining relationships (e.g., d tag for replaceable events)
7. Structuring content (e.g., subject tag for setting a title)
8. Group membership (e.g., h tag for associating events with a specific group)

Contributing

To add a new tag definition to this documentation, use the following command:

deno task generate_tag <tag_name> <nip_number>