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FEP-c0e0: Emoji reactions

Summary

This document describes how emoji reactions are implemented in ActivityPub network.

History

Misskey supports emoji reactions since version 10.97.0 (2019).
Pleroma supports emoji reactions since version 2.0.0 (2020).

Requirements

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC-2119.

EmojiReact activity

EmojiReact activity type is considered to be a part of LitePub vocabulary. Its full IRI is http://litepub.social/ns#EmojiReact.

This activity is similar to Like activity. In addition to standard properties of Like activity, EmojiReact activity MUST have a content property. Reaction content MUST be either a single unicode grapheme, or a shortcode of a custom emoji. The shortcode MUST be enclosed in colons.

If custom emoji is used, EmojiReact activity MUST have a tag property containing a single Emoji object (which is specified in Mastodon ActivityPub extension documentation). The value of its name property MUST be a shortcode that matches the shortcode in reaction content, and it SHOULD be enclosed in colons. The embedded Emoji can originate from a server that is different from the actor’s server.

An actor can generate multiple EmojiReact activities for a single object. However, implementers MAY choose to not allow more than one reaction with the same emoji, or more than one reaction per object.

Example with unicode emoji:

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "litepub": "http://litepub.social/ns#",
      "EmojiReact": "litepub:EmojiReact"
    }
  ],
  "actor": "https://alice.social/users/alice",
  "content": "🔥",
  "id": "https://alice.social/activities/65379d47-b7aa-4ef6-8e4f-41149dda1d2c",
  "object": "https://bob.social/objects/57caeb99-424c-4692-b74f-0a6682050932",
  "to": [
    "https://alice.social/users/alice/followers",
    "https://bob.social/users/bob"
  ],
  "type": "EmojiReact"
}

Example with custom emoji:

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "toot": "http://joinmastodon.org/ns#",
      "Emoji": "toot:Emoji",
      "litepub": "http://litepub.social/ns#",
      "EmojiReact": "litepub:EmojiReact"
    }
  ],
  "actor": "https://alice.social/users/alice",
  "content": ":blobwtfnotlikethis:",
  "id": "https://alice.social/activities/65379d47-b7aa-4ef6-8e4f-41149dda1d2c",
  "object": "https://bob.social/objects/57caeb99-424c-4692-b74f-0a6682050932",
  "tag": [
    {
      "icon": {
        "mediaType": "image/png",
        "type": "Image",
        "url": "https://alice.social/files/1b0510f2-1fb4-43f5-a399-10053bbd8f0f"
      },
      "id": "https://alice.social/emojis/blobwtfnotlikethis",
      "name": ":blobwtfnotlikethis:",
      "type": "Emoji",
      "updated": "2024-02-07T02:21:46.497Z"
    }
  ],
  "to": [
    "https://alice.social/users/alice/followers",
    "https://bob.social/users/bob"
  ],
  "type": "EmojiReact"
}

Like with content

Emoji reaction can also be represented as a Like activity. This variant of emoji reaction will processed by non-supporting implementations as a regular “like”, and when that is preferable, implementers MAY use Like type instead of EmojiReact type.

Implementations MUST process Like with content in the same way as EmojiReact activities.

Undo reaction

Emoji reactions can be retracted using a standard Undo activity:

{
  "@context": [
    "https://www.w3.org/ns/activitystreams"
  ],
  "actor": "https://alice.social/users/alice",
  "id": "https://alice.social/activities/99b8f47b-f3a9-4cf5-94a2-95352e7462d6",
  "object": "https://alice.social/activities/65379d47-b7aa-4ef6-8e4f-41149dda1d2c",
  "to": [
    "https://alice.social/users/alice/followers",
    "https://bob.social/users/bob"
  ],
  "type": "Undo"
}

`emojiReactions` collection

The list of emoji reactions to an object can be exposed using the emojiReactions property. Its full IRI is http://fedibird.com/ns#emojiReactions.

The URL specified by this property MUST resolve to a collection containing Like (with content) and EmojiReact activities.

Implementations

This document is based on implementations of emoji reactions in Misskey, Pleroma and Fedibird.

A number of other projects announced support for this FEP after it was published:

References

Christine Lemmer Webber, Jessica Tallon, ActivityPub, 2018
S. Bradner, Key words for use in RFCs to Indicate Requirement Levels, 1997
LitePub contributors, LitePub protocol suite, 2019
Mastodon contributors, Mastodon / ActivityPub, 2024

Copyright

CC0 1.0 Universal (CC0 1.0) Public Domain Dedication

To the extent possible under law, the authors of this Fediverse Enhancement Proposal have waived all copyright and related or neighboring rights to this work.

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