Nostr Relay Protocol Reference: The 8 NIP-01 Wire Messages

Nostr’s whole client-to-relay protocol fits on one page: eight JSON-array messages and one filter object. That minimalism is the point — it is why anyone can run a relay and why the network resists capture. This reference lays out every NIP-01 wire message with its exact syntax, the REQ filter fields and how they match, and the standardized rejection prefixes a relay speaks back. It completes our Nostr canon beside the NIPs index, the event-kinds reference and the standardized-tags reference.

Quick answer

The Nostr protocol is remarkably small: a client and a relay exchange just 8 message types, all JSON arrays. The client sends EVENT (publish), REQ (subscribe with filters) and CLOSE (unsubscribe); the relay replies EVENT (a matching event), OK (accepted/rejected), EOSE (end of stored events, real-time begins), CLOSED (subscription refused) and NOTICE (human-readable message). This reference lays out each message with its syntax and purpose, the REQ filter-object fields (ids/authors/kinds/#tag/since/until/limit) and their matching rules, and the 8 standardized machine-readable OK/CLOSED prefixes. Sourced from the canonical NIP-01.

The filter rule to remember: within one filter, all conditions must match (AND); across multiple filters in one REQ, an event passes if it matches ANY (OR). EOSE is the key signal — it tells the client "backfill done, the rest is live". AUTH is NOT here (that is NIP-42). Free CSV/JSON under CC BY 4.0; as of 2026-07-26.

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Client → relay messages 3

Message	Syntax	Purpose
`EVENT`	`["EVENT", <event JSON>]`	Publishes an event to the relay. The event is the full signed object (id, pubkey, created_at, kind, tags, content, sig).
`REQ`	`["REQ", <subscription_id>, <filters1>, <filters2>, ...]`	Requests stored events and subscribes to new ones. subscription_id is an arbitrary non-empty string up to 64 chars, scoped per connection; a new REQ with the same id replaces the old subscription.
`CLOSE`	`["CLOSE", <subscription_id>]`	Stops a previously opened subscription identified by subscription_id.

Relay → client messages 5

Message	Syntax	Purpose
`EVENT`	`["EVENT", <subscription_id>, <event JSON>]`	Sends an event matching a subscription. MUST carry a subscription_id from a REQ the client previously opened.
`OK`	`["OK", <event_id>, <true\|false>, <message>]`	Reports acceptance (true) or rejection (false) of a client EVENT. The 4th parameter MUST be present; it MAY be empty when true, otherwise MUST be a machine-readable prefix + ':' + human message.
`EOSE`	`["EOSE", <subscription_id>]`	End Of Stored Events: marks the boundary between stored events and real-time events newly streamed for that subscription.
`CLOSED`	`["CLOSED", <subscription_id>, <message>]`	Sent when the relay refuses or terminates a subscription from its side. Uses the same prefix:message convention as OK.
`NOTICE`	`["NOTICE", <message>]`	Sends a human-readable message (usually an error) to the client. NIP-01 defines no rules for how NOTICEs are sent or handled.

REQ filter-object fields

Field	Type	Meaning
`ids`	array of strings	Event ids to match. MUST contain exact 64-char lowercase hex (exact match; no prefix matching in current NIP-01).
`authors`	array of strings	The event pubkey must be one of these. MUST contain exact 64-char lowercase hex.
`kinds`	array of integers	The event kind must be in the list.
`#<single-letter>`	array of strings	Tag filter (e.g. #e = event ids, #p = pubkeys). Relays index single-letter tags; only the FIRST value of a tag is indexed. #e/#p MUST use exact 64-char lowercase hex. Event and filter must share at least one value.
`since`	integer (unix seconds)	Event created_at must be >= since.
`until`	integer (unix seconds)	Event created_at must be <= until. In short: since <= created_at <= until.
`limit`	integer	Max events the relay SHOULD return for the initial query only (ignored afterwards). Returns the newest n by created_at (ties broken by lowest id).

Standardized OK / CLOSED prefixes

duplicate: The event was already received / stored.

pow: The event does not meet a required proof-of-work difficulty.

blocked: The pubkey or event is blocked by relay policy.

rate-limited: The client is sending too fast.

invalid: The event or request is malformed / fails validation.

restricted: The action requires an authorization the client does not have.

mute: The event was accepted-but-ignored (e.g. nobody was listening).

error: Catch-all for when none of the other prefixes fit.

Source: the canonical NIP-01 from nostr-protocol/nips (fetched 2026-07-26). Completes the on-site Nostr canon alongside the NIPs, event kinds and standardized tags references — the fourth leg of the protocol canon.

Related products, repair, and setup paths

Last reviewed July 26, 2026.