Label
Labels attach short, structured strings to events, pubkeys, relays, or URLs to enable filtering, categorization, and machine-readable annotation. A label namespace (L tag) scopes its labels (l tags) to a defined vocabulary — such as an ISO standard or reverse-domain notation — making them unambiguous and queryable across clients and relays. Labels can be published as standalone Label events targeting any object, or added directly to any event kind for self-reporting.
Label Event (kind:1985)
Assigns one or more labels to a target event, pubkey, addressable event, or relay. Publishers SHOULD limit each event to a single namespace to avoid ambiguity when querying.
Required Tags
| Tag | Description |
|-----|-------------|
| l | The label value. MUST include a mark (third element) matching the L namespace if present; otherwise ugc is implied. |
| e / p / a / r | Target: event id, pubkey, addressable event (kind:pubkey:d-tag), or relay URL. At least one MUST be present. Relay hints SHOULD be included for e and p tags. |
Optional Tags
| Tag | Description |
|-----|-------------|
| L | Label namespace. RECOMMENDED for searchability; use ISO standards or reverse-domain notation (e.g. ISO-3166-2, com.example). The ugc namespace MAY be used for end-user-provided content. Namespaces starting with # associate the target with the label’s value as a standard nostr tag. |
Content
Short, meaningful label strings. Longer discussion or justification for the label goes in content.
Self-Reporting
l and L tags MAY be added to other event kinds to support self-reporting. For events
with a kind other than 1985, labels refer to the event itself.
Structured Label Types
For precise, machine-readable labelling, use a well-defined L namespace with l values that follow a consistent format. Each l tag MUST include a mark (third element) matching the L namespace. Below is a summary of known types and the event kinds they apply to.
| Type | L namespace | l value format | Event kinds |
|------|---------------|------------------|-------------|
| App capabilities | app | reads:audio/mpeg, writes:kind:1, alternative:Discord | kind:32267, kind:31990, kind:1985 |
| Geographic | ISO-3166-2 | IT-MI | any kind (self-label or kind:1985) |
| Language | ISO-639-1 | en | any kind (self-label or kind:1985) |
| Topic | #t | permies | pubkeys, events (kind:1985) |
For self-labelling, l and L tags are added directly to the target event. For third-party labelling via kind:1985, use an e, p, a, or r tag to identify the target. When using a tags for addressable events, the format is <kind>:<pubkey>:<d-tag>.
Example events
A suggestion that multiple pubkeys be associated with the permies topic.
{
"kind": 1985,
"tags": [
["L", "#t"],
["l", "permies", "#t"],
["p", <pubkey1>, <relay_url>],
["p", <pubkey2>, <relay_url>]
],
// other fields...
}Publishers can self-label by adding l tags to their own non-1985 events. In this case, the kind 1 event’s author
is labeling their note as being related to Milan, Italy using ISO 3166-2.
{
"kind": 1,
"tags": [
["L", "ISO-3166-2"],
["l", "IT-MI", "ISO-3166-2"]
],
"content": "It's beautiful here in Milan!",
// other fields...
}See Also
-
"Protocol" — Relay hints for
eandptags