Nostr is an open protocol for signed, relay-distributed events. Like Markdown, it has no single authority — most implementations converge on the same kind numbers for the same content types, but differ in which tags they support, which conventions they follow, and how they combine kinds into larger systems. This document describes our flavour: the event kinds, tags, and conventions used across these specs, with references to where each is defined in detail.

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

Keys and signatures use [Schnorr signatures over secp256k1](https://bips.xyz/340). The id is the SHA-256 of the UTF-8 JSON serialization of [0, pubkey, created_at, kind, tags, content] with no extra whitespace.

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

| Range | Behaviour | |-------|-----------| | 0, 3, 10000–19999 | Replaceable — only the latest event per pubkey + kind is kept. | | 1–9999 (excl. 0, 3) | Regular — all events stored. | | 20000–29999 | Ephemeral — not expected to be stored. | | 30000–39999 | Addressable — only the latest per pubkey + kind + d is kept. |

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

Kind Reference

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:

| Tag | Format | Use | |-----|--------|-----| | e | ["e", "<event-id>", "<relay-url?>", "<pubkey?>"] | Reference to a regular event | | p | ["p", "<pubkey>", "<relay-url?>"] | Reference to a user | | a | ["a", "<kind>:<pubkey>:<d>", "<relay-url?>"] | Reference to an addressable event | | d | ["d", "<slug>"] | Unique identifier for addressable events |

Tag Reference