Misskey — Complete Reference

Overview

Misskey is a free, open-source, decentralized microblogging platform — a feature-rich Japanese-origin Fediverse platform that predates many others. Created by syuilo (Eiji Shinoda) in 2014 as a BBS-style forum, it adopted ActivityPub in 2018. The name comes from the song "Brain Diver" by the band May'n. Licensed AGPL-3.0.

Misskey is explicitly not a Mastodon fork — it is "a project completely different from Mastodon or other alike projects." Its cultural DNA reflects Japanese social media preferences: emoji reactions as the primary engagement mechanism (not simple likes), rich visual formatting (MFM), integrated file management (Drive), and playful features like

isCat

As of late 2024: ~918,550 registered accounts, ~25,782 active users, 1,096+ instances. The flagship instance misskey.io is reportedly the second largest instance in the entire Fediverse. MisskeyHQ exists as a company entity, funded by donations and software licensing.

1. Technology Stack

Resource Footprint

Small instances: ~848 MB RAM with CPU bursts. A $10/month VPS suffices for small communities; $20/month for 15–50 users.

Repository

https://github.com/misskey-dev/misskey

2. ActivityPub Extensions

Misskey uses the JSON-LD namespace

https://misskey-hub.net/ns#

misskey

Extension Reference

_misskey_content

source

_misskey_summary

_misskey_quote

fedibird:quoteUri

as:quoteUrl

_misskey_reaction

:name:

_misskey_votes

replies.totalItems

_misskey_talk

true

isCat

_misskey_followedMessage

_misskey_requireSigninToViewContents

_misskey_makeNotesFollowersOnlyBefore

_misskey_makeNotesHiddenBefore

_misskey_license

freeText

Emoji Reactions Wire Format

Misskey's emoji reactions are the most significant interoperability concern. When a user reacts with an emoji, Misskey sends a

Like

_misskey_reaction

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {
      "misskey": "https://misskey-hub.net/ns#",
      "_misskey_reaction": "misskey:_misskey_reaction"
    }
  ],
  "type": "Like",
  "id": "https://misskey.example/likes/abc123",
  "actor": "https://misskey.example/users/alice",
  "object": "https://remote.example/notes/xyz",
  "_misskey_reaction": "👍",
  "content": "👍"
}

For custom emoji reactions:

{
  "type": "Like",
  "_misskey_reaction": ":blobcat:",
  "content": ":blobcat:",
  "tag": [
    {
      "type": "Emoji",
      "id": "https://misskey.example/emojis/blobcat",
      "name": ":blobcat:",
      "icon": {
        "type": "Image",
        "url": "https://misskey.example/files/blobcat.png"
      }
    }
  ]
}

Interoperability: Platforms that do not understand

_misskey_reaction

Like

content

Quote Posts Wire Format

{
  "type": "Note",
  "id": "https://misskey.example/notes/abc123",
  "content": "<p>My thoughts on this</p>",
  "_misskey_quote": "https://remote.example/notes/original",
  "quoteUrl": "https://remote.example/notes/original"
}

Both

_misskey_quote

quoteUrl

https://fedibird.com/ns#quoteUri

3. MFM (Misskey Flavored Markdown)

Proprietary markup language usable in notes, content warnings, usernames, and bios. General syntax:

$[name.attribute1,attribute2=value content]

Text Formatting

• Bold:

  **text**

• Small:

  <small>text</small>

• Center:

  <center>text</center>

• Quotes:

  > text

• Ruby:

  $[ruby text reading]

• Links:

  [label](url)

• Code: backticks (inline), triple backticks with language (blocks, 200+ languages via Shiki)

Visual Effects

$[flip text]

$[font.serif text]

$[blur text]

$[fg.color=hex text]

$[bg.color=hex text]

$[border.style=solid,width=4 text]

$[position.x=0.8,y=0.5 text]

$[rotate.deg=30 text]

$[scale.x=4,y=2 text]

$[x2]

$[x3]

$[x4]

Animations

$[jelly text]

$[tada text]

$[jump text]

$[bounce text]

$[spin text]

.left

.alternate

.x

.y

$[shake text]

$[twitch text]

$[rainbow text]

$[sparkle text]

All animations support

.speed=5s

Federation note: MFM is rendered as HTML when federating via ActivityPub. The

_misskey_content

source

4. Note System

Visibility Levels

public

home

followers

specified

Features

• Content Warning (CW):

  summary

  field hides content behind a toggle
• Renote: Boost/reblog (Announce activity)
• Quote Renote: Boost with added commentary (

  _misskey_quote

  )
• Polls:

  Question

  activity type with

  _misskey_votes

  for counts
• Reactions: Full emoji reactions (see Section 2)
• Mentions: @-mentions across the Fediverse
• Hashtags: Standard

  Hashtag

  tag type

Timelines

5. Unique Features

Drive

Cloud storage system for managing uploaded files. Files can be organized into folders and reused across multiple notes without re-uploading. Each file retains metadata (type, size, hash). Drive capacity is configurable per-user by instance administrators via role policies.

Antennas

Customizable filtered feeds that collect notes matching set conditions (keywords, users, file attachments) in real time. Essentially continuous background searches. Antennas exclude the user's own posts.

Deck UI

Multi-column layout with side-by-side views for an information-dense interface. Users can arrange timeline columns, notification panels, and other widgets freely.

Channels

Topic-based note collections within an instance. Similar to forums or discussion threads organized by subject.

Pages

Static page creation system using MFM and custom emoji, enabling users to build content beyond notes.

Other Features

• Clips — public/private categorized bookmarks
• Plugins — extend web client functionality via AiScript
• Themes — full client appearance customization
• Widgets — small interactive dashboard displays
• Webhooks — external service integration
• Word mute / Thread mute — content filtering
• Charts — server data visualization
• Online status — activity indicators on profile icons
• Share form — at

  /share

  path for social sharing buttons
• Safe mode — disables custom CSS, plugins, themes
• Embeds — embed notes and timelines on external websites

• isCat

  mode — users identify as cats with visual effects in supporting clients

6. API

REST API

All endpoints use HTTP POST (not GET for reads):

POST /api/notes/create
POST /api/notes/show
POST /api/users/show
POST /api/following/create

Authentication via access tokens. SDK:

misskey-js

Streaming API

WebSocket-based with channel multiplexing:

{
  "type": "connect",
  "body": {
    "channel": "homeTimeline",
    "id": "arbitrary-unique-id"
  }
}

Available channels:

globalTimeline

homeTimeline

hybridTimeline

localTimeline

main

Multiple channels can be multiplexed on a single WebSocket connection using different IDs.

7. Fork Ecosystem

Misskey has the most extensive fork tree in the Fediverse. All forks federate with each other and the broader Fediverse.

Active Forks

Discontinued / EOL Forks

Fork Relationship

Misskey (syuilo, 2014–)
├── Sharkey (soft fork, ACTIVE)
├── Cherrypick (soft fork, ACTIVE)
├── Meiskey (v11 fork, ACTIVE)
├── FoundKey (v12 hard fork, EOL)
└── Calckey (2022) → Firefish (2023, DISCONTINUED)
    ├── Iceshrimp → Iceshrimp.NET (C# rewrite)
    └── Catodon (DISCONTINUED)

Pattern: Forks emerge from (a) feature gaps upstream won't fill, (b) governance/communication issues, or (c) architectural changes (Iceshrimp.NET's language rewrite).

8. Misskey vs Mastodon

9. Interoperability Notes for Implementers

1. Emoji reactions arrive as

   Like

   activities — check for

   _misskey_reaction

   to distinguish a specific emoji reaction from a generic favourite. If absent, treat as a standard Like. The

   content

   field also contains the reaction value.

2. Custom emoji in reactions — when

   _misskey_reaction

   contains a

   :name:

   string, the

   tag

   array includes an

   Emoji

   object with the image URL. Display the custom emoji image if available, fall back to treating it as a Like.

3. Quote posts — Misskey sends

   _misskey_quote

   and

   quoteUrl

   on Note objects. Also check for

   fedibird:quoteUri

   (Fedibird/Mastodon compatibility). Display as an embedded quote if your platform supports it.

4. MFM content — notes from Misskey contain HTML in

   content

   (with MFM effects stripped) and optionally MFM source in the

   source

   property. Use the HTML for display; the MFM source is only useful if you want to re-render with a MFM parser (library:

   mfm-js

   ).

5. isCat

   property on actors — a boolean extension. Misskey-family clients show cat ears and modify text display for cat-mode users. Safe to ignore but do not strip when forwarding actor documents.

6. Chat messages — notes with

   _misskey_talk: true

   are Misskey chat messages. They federate as normal Notes to non-Misskey platforms. Display as regular posts if your platform has no chat feature.

7. All API endpoints use POST — unlike Mastodon's REST conventions, Misskey uses POST for everything including reads. If implementing a Misskey-compatible API, every endpoint must accept POST.

8. Visibility level "home" — Misskey has a fourth visibility level (

   home

   ) where notes are visible to everyone but excluded from the local and global timelines. This maps to ActivityPub

   to: followers, cc: Public

   (the inverse of Mastodon's "unlisted"). Handle carefully when federating.

9. Poll vote counts — Misskey includes

   _misskey_votes

   on poll options. This is equivalent to

   replies.totalItems

   but may be more reliably present. Prefer

   _misskey_votes

   when available.

10. Note content restrictions — the

    _misskey_makeNotesFollowersOnlyBefore

    and

    _misskey_makeNotesHiddenBefore

    properties on actors signal that historical content has access restrictions. Respect these when fetching older notes from Misskey actors.

10. Known Considerations

• No post editing in core Misskey — users must delete and redraft. The Sharkey fork adds federated note editing with version history.
• Cannot follow hashtags — use Antennas (keyword-filtered feeds) instead.
• No official mobile apps — third-party options include SocialHub (iOS) and Milktea (Android). The web client supports PWA.
• Antennas exclude personal posts from their results.
• Mute functionality gaps regarding mentions.
• No MRF equivalent for regex-based content filtering (unlike Pleroma/Akkoma).
• November 2025 announcement about potentially replacing ActivityPub with "Misskey's own low-overhead federation system" — details unclear, impact on interoperability unknown.
• Geographic registration restrictions on misskey.io — initially blocked Europeans (GDPR concerns), later restricted to Japanese users, Korea allowed since February 2026.
• Recent security fixes — CVE-2026-28431, CVE-2026-28432, CVE-2026-28433 patched in version 2026.3.1.