Nostrbook

Appearance

Tag: client ​

Overview ​

The client tag identifies the client application that published a Nostr event. It provides a way for users and applications to discover and potentially redirect to the client used to publish specific events.

Specification ​

PropertyValue
Tag Nameclient
Defined inNIP-89
Required forOptional for any event kind

Format ​

["client", "<client-name>", "<handler-event-identifier>", "<relay-hint>"]

Usage Description ​

When publishing events, clients may include a client tag to identify the application that published the note. The tag includes:

  1. <client-name>: The name of the client application
  2. <handler-event-identifier>: Address identifying a handler event, typically in the format 31990:<app-pubkey>:<d-identifier>
  3. <relay-hint>: A relay URL where the handler event can be found

This tag has privacy implications as it reveals which software the user is using to publish events, so clients should allow users to opt out of including this tag.

Examples ​

Basic Example ​

json
["client", "My Nostr Client"]

Extended Example with Handler Information ​

json
["client", "Zapstr", "31990:1743058db7078661b94aaf4286429d97ee5257d14a86d6bfa54cb0482b876fb0:abcd", "wss://relay.example.com"]

Client Behavior ​

Clients should:

  1. Optionally include this tag when publishing events to identify themselves
  2. Allow users to disable the inclusion of this tag for privacy reasons
  3. When reading events with this tag, optionally use the information to display which client created the event
  4. Potentially use the handler information to redirect users to the original client for better handling of specialized events

Relay Behavior ​

Relays should treat this tag like any other tag and propagate it without special handling.

References ​

  • [a tag (Used in kind:31989 events to reference handler applications)]
  • [k tag (Used in kind:31990 handler events to indicate supported event kinds)]

Notes ​

The client tag is part of the broader application handler framework described in NIP-89, which enables discovery and redirection to specialized applications that can handle specific event kinds. This system enhances interoperability between different Nostr clients and specialized applications.