Relay

A relay is a server that accepts signed Nostr events, stores them, and serves them to clients that subscribe with filters.

Why it matters

Relays are where decentralization actually lives or dies. Because clients read from many at once, no single relay is load-bearing — but if everyone converges on the same three, the property is theoretical.

A relay is also deliberately unintelligent. It does not resolve identity, thread conversations, or decide what a client should see. That work belongs to the client, which is why a relay can be a few hundred lines and why running one is within reach of an individual.

How it works

Clients connect over WebSocket and exchange JSON arrays. A client sends EVENT to publish, REQ with a subscription id and filters to ask for events, and CLOSE to end a subscription. The relay answers with EVENT for each match, EOSE when the stored events run out and the live feed begins, OK to accept or reject a publish, CLOSED when it ends a subscription itself, and NOTICE for human-readable messages.

A filter selects on ids, authors, kinds, single-letter tag fields such as #e and #p, and the since, until and limit bounds. Relays set their own policies — open, paid, whitelisted or topic-scoped — and describe themselves in the relay information document defined by NIP-11.

Sources

• https://github.com/nostr-protocol/nips/blob/master/01.md
• https://github.com/nostr-protocol/nips/blob/master/11.md