The Event

Every object on Nostr is an event — a signed JSON structure with the following fields:

{
  "id":         "<32-byte lowercase hex sha256 of the serialized event>",
  "pubkey":     "<32-byte lowercase hex public key of the author>",
  "created_at": "<unix timestamp in seconds>",
  "kind":       "<integer 0–65535>",
  "tags":       [["<tag-name>", "<value>", "..."], "..."],
  "content":    "<arbitrary string>",
  "sig":        "<64-byte lowercase hex Schnorr signature over id>"
}

Keys and signatures use Schnorr signatures over secp256k1. The id is the SHA-256 of the UTF-8 JSON serialization of [0, pubkey, created_at, kind, tags, content] with no extra whitespace.

Kinds

The kind integer tells clients and relays how to interpret an event. Ranges carry structural meaning:

When two replaceable or addressable events share the same timestamp, the one with the lexically lower id wins.

Tags

Tags are arrays of strings attached to an event. The first element is the tag name; the second is the primary value. Single-letter tag names (a–z, A–Z) are indexed by relays, enabling filter queries like {"#e": ["<event-id>"]}. Multi-word tag names are not relay-indexed.

The four universal single-letter tags used across all kinds: