NIP-66 tag reference for relay monitoring events

NIP-66 relay monitoring events use a defined set of tags to encode relay health, capabilities, and metadata. This page documents every tag used across the three NIP-66 event kinds: kind 10166 (monitor announcement), kind 30166 (relay status), and kind 1066 (relay status delta). For background on the event kinds themselves, see NIP-66 event kinds.

Kind 10166 tags — Monitor Announcement

These tags appear in kind 10166 events published by monitors to describe their configuration and capabilities.

Tag	Values	Required	Description
`frequency`	seconds, e.g. `3600`	Yes	How often this monitor checks relays
`n`	`clearnet`, `tor`, `i2p`	Yes	Networks this monitor covers — one tag per network
`c`	`open`, `read`, `write`, `ssl`, `dns`, `geo`, `info`	Yes	Check types performed — one tag per check type
`timeout`	check name + ms, e.g. `open`, `5000`	No	Timeout for the named check (multi-value tag)
`k`	kind number, e.g. `30166`	No	Event kinds this monitor publishes
`g`	geohash, e.g. `u4pruyd`	No	Geohash of the monitor’s physical location

frequency

string

required

Check interval in seconds as a string. A monitor with ["frequency", "3600"] checks relays every hour. Use this to determine how stale monitor data may be.

string

required

Network type the monitor covers. One tag per network. Valid values: clearnet, tor, i2p.

string

required

Check type performed. One tag per check. Valid values:

open — can the monitor open a WebSocket connection?
read — does the relay respond to REQ messages?
write — does the relay accept EVENT messages?
ssl — is the TLS certificate valid?
dns — does the hostname resolve?
geo — what is the relay’s geographic location?
info — what does the NIP-11 info document say?

timeout

string

Multi-value tag. First value is the check name; second is the timeout in milliseconds as a string. Example: ["timeout", "open", "5000"].

string

Event kinds this monitor publishes as a result of its checks. Typically 30166 and optionally 1066.

string

Geohash of the monitor’s physical location. Used for geographic coverage analysis. Longer geohashes indicate more precision.

Kind 30166 tags — Relay Status

These tags appear in kind 30166 events, which are the primary relay status events. One event exists per (relay URL, monitor pubkey) pair.

Tag	Values	Required	Description
`d`	relay URL	Yes	Addressable identifier — makes this event parameterized replaceable
`r`	relay URL	Yes	Queryable relay URL (used in `#r` filter)
`n`	`clearnet`, `tor`, `i2p`	Yes	Network type of this relay
`R`	capability flag	No	Relay capability/requirement flag (see R tag below)
`rtt-open`	milliseconds	No	Round-trip time for WebSocket open in ms
`rtt-read`	milliseconds	No	Round-trip time for read check in ms
`rtt-write`	milliseconds	No	Round-trip time for write check in ms
`N`	NIP number	No	Supported NIP — one tag per NIP
`k`	kind number	No	Supported event kind — one tag per kind, max 21
`p`	hex pubkey	No	Relay operator pubkey (from NIP-11)
`s`	software name	No	Relay software name (from NIP-11 `software` field)
`L`	namespace	No	Label namespace declaration (NIP-32)
`l`	value + namespace	No	Label value in the declared namespace (NIP-32)

string

required

The relay’s WebSocket URL. Serves as the d tag for parameterized replaceability: only the most recent event per (pubkey, d tag) is retained on relays.

string

required

The relay’s WebSocket URL, also stored as a queryable r tag. Use #r in REQ filters to match this tag.

string

required

Network type of the relay being monitored. One of clearnet, tor, or i2p.

string

Relay capability flag. Values without a ! prefix are active; values with ! are not active.

Value	Meaning
`open`	Accepted a WebSocket connection
`read`	Responded to REQ
`write`	Accepted EVENT
`ssl`	TLS certificate is valid
`auth`	Requires NIP-42 auth
`payment`	Requires payment
`pow`	Requires proof of work
`!auth`	Does not require auth
`!payment`	Does not require payment
`!pow`	Does not require proof of work

rtt-open

string

Round-trip time for the WebSocket open check in milliseconds, as a string. Example: ["rtt-open", "120"].

rtt-read

string

Round-trip time for the read check in milliseconds, as a string.

rtt-write

string

Round-trip time for the write check in milliseconds, as a string.

string

A NIP number supported by this relay, as a string. One tag per NIP. Example: ["N", "42"]. Query with '#N': ['42'].

string

An event kind supported by this relay, as a string. One tag per kind, with a maximum of 21 kinds listed. Example: ["k", "1"].

string

The relay operator’s Nostr pubkey in hex, sourced from the NIP-11 info document’s pubkey field.

string

The relay software name sourced from the NIP-11 software field. Examples: strfry, nostr-rs-relay, nostream.

string

NIP-32 label namespace declaration. Paired with one or more l tags that declare values in this namespace. Example: ["L", "ISO-639-1"].

string

NIP-32 label value in a declared namespace. Two values: the label and the namespace. Example: ["l", "en", "ISO-639-1"]. Also used for NIP-66 version labeling: ["l", "draft7", "nip66.draft"].

Kind 1066 tags — Relay Status Delta

Kind 1066 events use a subset of kind 30166 tags. Only tags that changed since the last status event are included.

Tag	Values	Description
`r`	relay URL	Which relay this delta applies to
`R`	capability flags	Changed requirement/capability flags
`rtt-open`	milliseconds	Changed open latency
`rtt-read`	milliseconds	Changed read latency
`rtt-write`	milliseconds	Changed write latency
`N`	NIP number	Changed NIP support

Content field by kind

Kind	Content	Format
10166	Empty string	—
30166	NIP-11 info document	JSON string — parse with `JSON.parse()`
1066	Empty or partial NIP-11 diff	JSON string

The kind 30166 content contains the relay’s self-reported NIP-11 information document. Always validate and sanitize this data — it comes from the relay operator, not the monitor.

// Parsing the NIP-11 content from a kind 30166 event
function parseRelayInfo(event) {
  if (!event.content) return null
  try {
    return JSON.parse(event.content)
  } catch {
    return null // Content may be empty or invalid JSON
  }
}

const info = parseRelayInfo(event)
if (info) {
  console.log('Software:', info.software)
  console.log('Supported NIPs:', info.supported_nips)
  console.log('Limitation:', info.limitation)
}

REQ filter patterns

NIP-01 REQ filters support tag matching with the #<tag-letter> syntax. Tag filter values are always strings, even when the tag contains a number.

// Filter by network
{ kinds: [30166], '#n': ['clearnet'] }

// Filter by capability flags
{ kinds: [30166], '#R': ['!auth', '!payment'] }

// Filter by NIP support
{ kinds: [30166], '#N': ['42'] }

// Filter by software
{ kinds: [30166], '#s': ['strfry'] }

// Filter by relay URL (d tag)
{ kinds: [30166], '#d': ['wss://relay.damus.io'] }

// Filter by relay URL (r tag, queryable in 1066)
{ kinds: [1066], '#r': ['wss://relay.damus.io'] }

// Combine multiple filters (AND logic)
{
  kinds: [30166],
  '#n': ['clearnet'],
  '#R': ['!auth'],
  '#N': ['42'],
  '#s': ['strfry'],
}

Multiple values within a single tag filter use OR logic: '#n': ['clearnet', 'tor'] matches events with either clearnet or tor. Multiple separate tag filters use AND logic: '#n': ['clearnet'], '#R': ['!auth'] matches events that are clearnet and do not require auth.

REST API

NIP-66 Protocol

CVM Tools

NIP-66 tag reference for relay monitoring events

Kind 10166 tags — Monitor Announcement

Kind 30166 tags — Relay Status

Kind 1066 tags — Relay Status Delta

Content field by kind

REQ filter patterns

Build docs developers (and LLMs) love

REST API

NIP-66 Protocol

CVM Tools

Documentation Index

​Kind 10166 tags — Monitor Announcement

​Kind 30166 tags — Relay Status

​Kind 1066 tags — Relay Status Delta

​Content field by kind

​REQ filter patterns

Build docs developers (and LLMs) love

Kind 10166 tags — Monitor Announcement

Kind 30166 tags — Relay Status

Kind 1066 tags — Relay Status Delta

Content field by kind

REQ filter patterns