| name | kb-friendica |
| description | Background knowledge about Friendica, the federated social networking platform (Facebook alternative). Covers Friendica's history and lineage (Mistpark 2010, Friendika, Friendica, the Red Matrix/Hubzilla fork), its multi-protocol architecture (ActivityPub, DFRN, Diaspora protocol simultaneously), the DFRN protocol (Distributed Friends and Relations Network — Atom/ActivityStreams XML with public-key crypto handshake, dfrn_notify/dfrn_poll/dfrn_request endpoints), the ActivityPub implementation (Receiver/Processor/Transmitter classes, APDelivery workers, Mastodon-compatible API), the Diaspora protocol integration (reverse-engineered PHP implementation), the addon/plugin system (hook-based with 100+ hooks, Smarty3 templates, module intercept), cross-network connectors (Bluesky bidirectional, Tumblr, GNU Social, email IMAP/SMTP, RSS/Atom, WordPress/LiveJournal/Dreamwidth post-only), privacy controls (ACLs, Circles/Groups, multiple profiles, per-post permissions), content model (200,000-char posts, BBCode, photo albums, events, forums, polls), the database schema (97 tables, hub-and-spoke post model with post/post-user/post-content/post-media separation), the 8-layer architecture (Client/Frontend/Application/Business Logic/ Content Processing/Federation/Data/Background Worker), the tech stack (PHP, MySQL/MariaDB/PostgreSQL, Apache/Nginx, Smarty3, Composer, AGPL-3.0), supported FEPs (group federation, OpenWebAuth, long-form text, FEP-67ff), federation interoperability quirks (bridge role between protocol ecosystems, OStatus dropped in 2024.12), and the relationship to Mike Macgirvin's later projects (Hubzilla, Zot/Nomad protocol, Streams, Forte). Load when the user asks about Friendica federation; implementing a Friendica-compatible ActivityPub server; the DFRN protocol; how Friendica bridges multiple protocol ecosystems; Friendica's addon system; Friendica's privacy model; interoperating with Friendica instances; Friendica's Mastodon API compatibility; the Friendica-to-Hubzilla lineage; or cross-posting from Friendica to Bluesky, Tumblr, Diaspora, or other networks.
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| user-invocable | false |
Friendica — Complete Reference
Overview
Friendica is a free, open-source, decentralized social networking platform
— the Fediverse's answer to Facebook. Created by Mike Macgirvin (former
Netscape/AOL/Sun messaging engineer) in July 2010 under the original name
"Mistpark," it is one of the oldest continuously active Fediverse projects,
predating Mastodon by six years. Licensed AGPL-3.0.
Friendica's defining characteristic is its multi-protocol bridge role.
It simultaneously speaks ActivityPub, the Diaspora protocol, and its native
DFRN protocol, and connects (via addons) to Bluesky, Tumblr, GNU Social,
email (IMAP/SMTP), and RSS/Atom feeds. Fedi.Tips calls it "a sort of Swiss
Army knife of the Fediverse." Where Mastodon is a Twitter replacement
(microblogging), Friendica is a Facebook replacement (full social networking)
with Circles/Groups, photo albums, events, forums, 200,000-character posts,
and fine-grained ACL-based privacy controls.
Current maintainers are Tobias Diekershoff (FSFE) and Michael Vogel. As of
2025: ~220 active instances, ~20,800 registered users, ~2.8 million
statuses, 27,000+ commits from 250+ contributors.
1. History and Lineage
| Date | Event |
|---|
| July 2010 | Mike Macgirvin creates Mistpark in Australia, motivated by "Quit Facebook Day" privacy concerns |
| Mid-2010 | Within first month: federation with StatusNet (OStatus), RSS, email integration |
| Late 2010 | Renamed to Friendika |
| July 2011 | Zot protocol first named (Macgirvin's next-gen protocol design) |
| Sep 2011 | Macgirvin forks as "Free-Friendika" (MIT license) |
| Oct 2011 | Name changed to Friendica |
| Jan 2012 | First "Friendica" release (v2.37) |
| 2012 | Diaspora protocol reverse-engineered from scratch (~6 months) |
| May 2012 | Macgirvin departs, forks into Red / Friendica Red (MIT) |
| 2012-2013 | Red becomes Red Matrix |
| May 2015 | Red Matrix renamed to Hubzilla |
| Dec 2018 | ActivityPub support shipped |
| May 2023 | Initial Bluesky connector |
| Dec 2023 | Bidirectional Bluesky; Circles and Channels introduced |
| Jan 2025 | v2024.12: OStatus dropped, Prometheus metrics, FEP-67ff |
| Jan 2026 | v2026.01 "Blutwurz": reworked hook system, media embedding overhaul |
The Fork Lineage
Mistpark (2010)
└─> Friendika (2010) ─> Friendica (2011, AGPL-3.0)
└─> Free-Friendika (2011, MIT)
└─> Red / Friendica Red (2012)
└─> Red Matrix (2013)
└─> Hubzilla (2015, Zot protocol)
└─> Osada, Zap, Roadhouse (2018-2022)
└─> Streams (2021-present, Nomad protocol)
└─> Forte (2024, ActivityPub-only)
Founding Motivation
Macgirvin left Facebook in early 2010 and found no decentralized alternative
with both Facebook-like interactivity and privacy. StatusNet's OStatus had
"absolutely nothing in the way of privacy." He created the DFRN protocol to
address four gaps:
- No protocol for friend connections
- No privacy support in social protocols
- No cross-server wall posting
- Private media required sending copies to all recipients
2. Technology Stack
| Layer | Technology |
|---|
| Backend language | PHP (7.4+, 8.x recommended, supports 8.5) |
| Database | MariaDB (recommended), MySQL, PostgreSQL 9.6+ |
| Web server | Apache (mod-rewrite) or Nginx |
| Template engine | Smarty3 |
| Dependency management | Composer |
| DI container | Dice |
| Themes | frio (default), vier, quattro |
| License | AGPL-3.0 |
| Hardware minimum | 2 GB RAM |
| Required PHP extensions | Curl, GD, GMP, PDO, mbstring, Intl, MySQLi, OpenSSL, POSIX |
Entry Points
- Web:
index.php → App::processRequest()
- CLI:
bin/console.php → App::processConsole()
- Worker:
bin/console.php worker (or legacy bin/worker.php)
Configuration Hierarchy (increasing priority)
static/defaults.config.php — system defaultsstatic/settings.config.php — admin-configurable defaultsconfig/local.config.php — instance-specific overridesconfig database table — runtime settings (highest)
3. Federation Protocols
Friendica is unique in speaking multiple federation protocols
simultaneously, acting as a bridge between otherwise-separate ecosystems.
Currently Supported
| Protocol | Purpose | Since |
|---|
| ActivityPub | Federation with Mastodon, Pleroma, Pixelfed, PeerTube, Lemmy, etc. | Dec 2018 |
| Diaspora protocol | Federation with Diaspora pods, Hubzilla | 2012 |
| DFRN | Native Friendica-to-Friendica federation | July 2010 |
| WebFinger | User discovery | — |
| HTTP Signatures | Request authentication for ActivityPub | — |
| NodeInfo | Server metadata discovery | — |
| Salmon | Message exchange for replies and mentions | — |
Dropped
| Protocol | Dropped | Reason |
|---|
| OStatus (PubSubHubbub + Atom) | v2024.12 | Too few active OStatus-only servers |
Supported FEPs
Nine FEPs including: group federation (Lemmy/Kbin compatible), OpenWebAuth
(Hubzilla login), long-form text (partial), application actor identification,
object links, and FEP-67ff (FEDERATION.md).
4. The DFRN Protocol
Distributed Friends and Relations Network — Friendica's native protocol
for Friendica-to-Friendica federation. Creates an authenticated pipe between
users using public-key cryptography.
Message Format
- Atom Syndication Protocol wrapper with ActivityStreams 1.0, threading,
and media extensions
- Content in BBCode internally
- Specification:
spec/dfrn2.pdf in the Friendica repository
Key Concepts
- Distinguishes author (content creator) from owner (profile host)
- Communication boundary is the individual's profile page
- "Friends of friends" are visible, but direct contact required for
communication with third parties
Endpoints
| Endpoint | Purpose |
|---|
dfrn_request | Friend/contact requests |
dfrn_notify | Delivery (push) |
dfrn_poll | Feed retrieval (pull) |
Handshake
- Remote site POSTs to
dfrn_poll with type=profile-check
- Includes duplex direction, relationship
dfrn_id, and a random number
encrypted with the site's DFRN public key
- Original site decodes
dfrn_id, verifies relationship, decodes challenge,
matches sec string
Delivery Model
- Public messages: dual path — BBCode to DFRN clients + HTML conversion
with PubSubHubbub notification
- Private messages: direct delivery via
dfrn_notify to recipients only;
public hubs remain uninformed
- Polling:
src/Worker/OnePoll.php with configurable intervals (up to
5-minute checks)
- Retry: failed deliveries are queued for automatic retry
5. ActivityPub Implementation
Architecture
Three main classes in src/Protocol/ActivityPub/:
| Class | Role |
|---|
| Receiver | HTTP Signature verification, activity validation, JSON decoding |
| Processor | Activity type handling (Create, Update, Delete, Like, Announce) |
| Transmitter | JSON-LD generation for outbound activities |
Delivery: Worker/Notifier calculates recipients by protocol, spawning
APDelivery workers for ActivityPub contacts.
Supported Features
- Follow/unfollow accounts
- Public and non-public messaging
- Posting, commenting, liking, unliking, deletion
- Bidirectional comment distribution (thread-based and per-posting models)
- Thread completion (prevents conversation fragmentation)
- Failed delivery retry queuing
- Sends Follow for root post IDs to request inclusion in receiver collections
Known Limitations
- No native direct messages via ActivityPub (workaround: non-public post
restricted to single recipient)
- No account migration between nodes via ActivityPub
Mastodon-Compatible API
Extensive coverage:
- Accounts: verify_credentials, follow/unfollow/block/unblock/mute/unmute,
followers, following, relationships, search
- Statuses: create/get/delete, favourite/unfavourite, reblog/unreblog,
bookmark, pin/unpin, context
- Timelines: home, public, tag, list, direct
- Notifications: list, get, clear, dismiss
- Other: conversations, lists, media, search v1/v2, instance info,
follow requests, emojis, directory, polls, push subscriptions
Not implemented: profile updates via API, familiar followers, trending,
poll voting, streaming, admin functions, domain blocks
Compatible clients: Tusky, Fedilab, Sengi, Twidere, AndStatus, Bitlbee,
Raccoon for Friendica.
6. Cross-Network Connectivity
Built-in (no addon needed)
| Network | Protocol |
|---|
| Mastodon, Pleroma, Pixelfed, PeerTube, Lemmy, Kbin, Misskey | ActivityPub |
| Diaspora, Hubzilla, Socialhome | Diaspora protocol |
| Other Friendica nodes | DFRN |
| Email | IMAP4rev1 / ESMTP (bidirectional) |
| Any website/blog | RSS/Atom feed import |
Addon Connectors (bidirectional)
| Network | Notes |
|---|
| Bluesky | No API key needed; bidirectional since v2023.12 |
| pump.io | Posting, relaying, reading |
| GNU Social | Via statusnet addon |
Addon Connectors (post-only)
Tumblr, WordPress (XMLRPC), LiveJournal, Dreamwidth, InsaneJournal,
Libertree, Blogger, Buffer
Deprecated
- Twitter — removed due to API changes under Musk
- Facebook/Google+ — removed when APIs shut down
7. Privacy and Access Control
Friendica's privacy model is significantly more granular than most Fediverse
platforms:
- Posts default to private (configurable by admin to default public)
- Access Control Lists (ACLs) on every post via lock icon UI
- Circles (formerly Groups) for organizing contacts into permission sets
- Per-post overrides: select specific individuals or Circles to
allow/deny
- Multiple profiles: different profiles for different audiences (family,
friends, public)
- Anonymous profile viewing can be disabled
- Post deletion triggers removal notifications to all recipients
- Content expiration with automated removal from remote Friendica servers
Cross-Network Limitation
Privacy only fully works within Friendica's native protocols. Posts
shared via ActivityPub or other protocols lose fine-grained ACL enforcement
— the receiving server controls display. Private photo sharing only works
reliably between Friendica members.
Once published, post permissions CANNOT be changed.
8. Content Model
Post Capabilities
| Feature | Details |
|---|
| Maximum length | 200,000 characters |
| Markup | BBCode (bold, italic, headings h1-h6, code blocks, tables, spoilers, lists) |
| Media | Images (with alt text, dimensions), video (YouTube/Vimeo/generic), audio, OEmbed |
| Albums | Photo albums with tagging and per-album privacy |
| Events | Date, time, location, RSVP |
| Forums | Public and private, federated |
| Polls | Limited (not supported via Diaspora protocol) |
| Notes | Private notebook (notes to self) |
| Maps | By address, coordinates, or post location |
| Abstract/summary | Per-network overrides (e.g., [abstract=twit] for Twitter-length) |
Object Types
Friendica represents posts as ActivityPub Note objects when federating
via ActivityPub. Internally, content is stored in BBCode and converted to
HTML or ActivityPub JSON as needed for each protocol.
9. Database Schema
97 tables, utf8mb4 charset. Schema version tracked by
DB_UPDATE_VERSION.
Hub-and-Spoke Content Model
| Table | Purpose |
|---|
item-uri | URI registry for deduplication |
post | Protocol-agnostic metadata (author-id, owner-id, created) |
post-user | Per-user states (starred, hidden, visibility) |
post-content | Body text |
post-media | Attachments with MIME types |
post-thread / post-thread-user | Thread structure |
post-history | Edit history |
post-delivery / post-delivery-data | Delivery tracking |
post-tag / post-category | Tags and categories |
post-question / post-question-option | Polls |
delayed-post | Scheduled posts |
A single post can be visible to multiple users with different permission
levels without duplicating content — the post-user table stores per-user
state separately from post-content.
Contact Tables
| Table | Purpose |
|---|
contact | Both local and remote actors |
apcontact | ActivityPub-specific contact data |
fcontact | Diaspora-specific contact data |
contact-relation | Relationship graph |
user-contact | Per-user contact settings |
Relationship Constants
NOTHING=0, FOLLOWER=1, SHARING=2, FRIEND=3, SELF=4
Server/Federation Tables
gserver (known servers), endpoint (AP endpoints), inbox-status
(AP inbox tracking), diaspora-interaction (signed Diaspora interactions)
10. Architecture
8-Layer Model
- Client Layer — browsers, mobile apps (Raccoon, Fedilab), third-party
clients via Mastodon API
- Frontend Layer — theme system (frio/vier/quattro), JavaScript,
localization
- Application Layer — Router with 600+ routes
(
static/routes.config.php), modules, API endpoints
- Business Logic Layer — Model classes:
Item, Contact, User
- Content Processing Layer — BBCode formatting, media processing, URL
parsing
- Federation Layer —
Friendica\Protocol\ActivityPub,
Friendica\Protocol\Diaspora, Friendica\Protocol\DFRN
- Data Layer — Database abstraction (
DBA), schema management
(DBStructure)
- Background Processing — Worker queue with priority levels
Worker Queue
| Priority | Value |
|---|
| CRITICAL | 10 |
| HIGH | 20 |
| MEDIUM | 30 |
| LOW | 40 |
| NEGLIGIBLE | 50 |
Tasks enqueued via Worker::add() into workerqueue table. Default 10
parallel instances. Worker/Notifier routes deliveries to protocol-specific
workers (APDelivery, Delivery).
Namespaces
Friendica\Module, Friendica\Model, Friendica\Protocol,
Friendica\Worker, Friendica\Core, Friendica\Database, Friendica\Util
Dependency Injection
Dice DI container. Services accessed via static DI class: DI::dba(),
DI::config(), DI::logger(), DI::session(), DI::baseUrl(),
DI::l10n().
11. Addon/Plugin System
Hook-based architecture with 100+ hooks. Addons live in addon/ directory,
each in its own subdirectory.
Required Functions
function <addon>_install() {
\Friendica\Core\Hook::register($hookname, $file, $function);
}
function <addon>_uninstall() { }
Callback Signature
function <addon>_<hookname>(App $a, &$b) { }
$a is the Friendica App class; $b is hook-specific data passed by
reference.
Major Hook Categories
| Category | Hooks |
|---|
| Content | post_local, post_local_end, post_remote, display_item, prepare_body |
| Auth | authenticate, logged_in, register_post |
| Profile | profile_post, profile_edit, profile_sidebar |
| Contacts | follow, unfollow, revoke_follow, block, unblock |
| Settings | addon_settings, connector_settings |
| System | init_1, load_config, route_collection |
| Federation | probe_detect, item_by_link |
Module Intercept
Addons can act as full page modules by defining:
function <addon>_module() {}
function <addon>_content(App $a) {}
Notable Addons
- Cross-posting: bluesky, tumblr, diaspora, discourse, wppost,
ljpost, dwpost
- Storage: s3_storage, webdav_storage
- Auth: ldapauth, saml, keycloakpassword
- Privacy: securemail (GPG-encrypted notifications)
- Filters: advancedcontentfilter, langfilter, nsfw, superblock
12. Installation and Deployment
Methods
- Git clone:
git clone -b stable + composer install --no-dev +
web installer
- CLI:
bin/console autoinstall with config file or env vars
- Docker:
docker pull friendica (official image)
- YunoHost: app package available
Critical Requirements
- Cron every 5-10 minutes:
bin/worker.php (or daemon mode)
- HTTPS/TLS mandatory
- Must be at top-level domain or subdomain (not directory path) for
Diaspora federation
- Domain cannot be changed after installation
Scaling
- Nginx preferred over Apache (~2x capacity)
- Database tuning via mysqltuner.pl
- PHP-FPM for faster processing
- Configurable worker queue parallelism (default 10)
- Extended poller intervals (30-60 min) for large instances
13. Federation Interoperability
Friendica as Protocol Bridge
Friendica's unique value is connecting users across protocol boundaries:
Mastodon user ←─ActivityPub─→ Friendica ←─Diaspora protocol─→ Diaspora pod
↕
DFRN native
↕
Bluesky (addon)
↕
RSS/Atom/Email/Tumblr
A Friendica user can follow a Mastodon account, a Diaspora contact, a
Bluesky account, and an RSS feed — all in the same timeline.
vs. Mastodon
| Feature | Friendica | Mastodon |
|---|
| Post length | 200,000 chars | 500 chars |
| Protocols | AP + Diaspora + DFRN + addons | AP only |
| Contact groups | Circles with ACLs | Lists (no ACLs) |
| RSS reader | Built-in | No |
| Photo albums | Yes | No |
| Events/calendar | Yes | No |
| Quote posts | Yes (early pioneer) | Added later |
| Forums | Yes (public + private) | No |
| BBCode | Yes | No |
Known Issues
- Friendica's rich content (BBCode formatting, long posts) may be
truncated or stripped by Mastodon's HTML filtering
- Privacy ACLs only enforceable within Friendica — remote servers
control their own display
- Private photos only reliable between Friendica members
- Comment counts may be inaccurate on remote instances due to
incomplete thread federation
14. Governance and Community
- No corporation, foundation, or board — informal volunteer governance
- Core maintainers: Tobias Diekershoff (FSFE), Michael Vogel
- Communication: Friendica forums (dogfooding the platform)
- Code: GitHub + self-hosted Gitea at git.friendi.ca
- Mascot: Flaxy O'Hare (rabbit, CC0)
- Release cadence: quarterly stable releases, year.month versioning
- No direct donations accepted — covers server costs only
15. Common Implementation Mistakes
- Assuming Friendica only speaks ActivityPub: Friendica may deliver
content via DFRN or Diaspora protocol depending on the contact type —
inspect the contact's protocol, not just the server software
- Not handling long posts: Friendica posts can be up to 200,000
characters — truncate gracefully rather than rejecting
- Ignoring BBCode in content: Friendica's native format is BBCode,
converted to HTML for ActivityPub — the HTML may contain richer
formatting than typical Mastodon posts
- Expecting Mastodon API parity: Friendica's Mastodon API has gaps
(no streaming, no admin API, no poll voting) — test against a real
Friendica instance
- Not supporting the
Application instance actor: Friendica uses an
instance-level actor for some federation tasks — verify keys from
Application actors, not just Person
- Dropping unknown properties: Friendica posts may include properties
from DFRN or Diaspora context — ignore unknown properties rather than
rejecting the entire object
- Assuming public-by-default: Friendica defaults to private posts
(admin-configurable) — a Friendica instance may send fewer public
posts than expected
