Misskey Extensions to ActivityPub

This page documents the extensions to ActivityPub that Misskey uses. This page lists some context items defined in JSON-LD contexts and explains their semantics.

This document uses compact IRIs. The prefix ap is used to refer to https://www.w3.org/ns/activitystreams#. The prefix misskey is used to refer to https://misskey-hub-net/ns#.


  • compact IRI: misskey:_misskey_content
  • canonical IRI: https://misskey-hub.net/ns#_misskey_content

This value is deprecated and might be removed in the future. See also https://github.com/misskey-dev/misskey/pull/8787.

This value is identical to having a source property like this:

source: {
    content: _misskey_content,
    mediaType: "text/x.misskeymarkdown"

Where _misskey_content represents the value of the field described in this section.


  • compact IRI: misskey:_misskey_summary
  • canonical IRI: https://misskey-hub.net/ns#_misskey_summary

Used on actors to display their summary as MFM. The content is same as summary, but in MFM form.


  • compact IRI: misskey:_misskey_quote
  • canonical IRI: https://misskey-hub.net/ns#_misskey_quote

Ways to potentially provide this information using the core ActivityPub vocabulary are currently underway, see https://github.com/misskey-dev/misskey/issues/8722.

Indicates that this note is quoting another note. It contains the id of the note being quoted.

This seems to be identical to https://fedibird.com/ns#quoteUri. Misskey also uses as:quoteUrl for this but this was not adopted to the ActivityPub specification. This is for compatibility with some other ActivityPub programs that operate using this.


  • compact IRI: misskey:_misskey_reaction
  • canonical IRI: https://misskey-hub.net/ns#_misskey_reaction

Misskey federates its reactions as Like activities. What kind of reaction was used is conveyed using this field. Misskey also sets ap:content of the Like activity to the same value.

The content will be a string that either contains a single Unicode Emoji or a string that starts and ends with a colon. In the latter case the reaction uses a custom emoji, and the tag property will be set to contain the data of the respective emoji.


  • compact IRI: misskey:_misskey_votes
  • canonical IRI: https://misskey-hub.net/ns#_misskey_votes

This value is used for Question activities to indicate the number of votes an option currently has. This value is identical to having a replies property like this:

replies: {
    type: 'Collection',
    totalItems: _misskey_votes

Where _misskey_votes represents the value of the field described in this section.


  • compact IRI: misskey:_misskey_talk
  • canonical IRI: https://misskey-hub.net/ns#_misskey_talk

This value is used for Note type objects to indicate that they are a Misskey chat message. Misskey handles these kinds of messages specially, e.g. it will apply different audience scoping rules and show them via a different API than usual Note objects.

This field can only take the value of true (or be absent).


  • compact IRI: misskey:isCat
  • canonical IRI: https://misskey-hub.net/ns#isCat

Used on actors to indicate that they in some way identify as a cat, expressed as a boolean value. If this property is set to true, displaying the actor or their notes will have some special effects attached in some clients.