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Background knowledge about PieFed, the federated link aggregation and discussion platform (Python-based Reddit/Lemmy alternative in the Threadiverse). Covers PieFed's tech stack (Python/Flask, PostgreSQL, Celery/Redis, htmx, Jinja2, AGPL-3.0), the Lemmy-compatible ActivityPub implementation (Community as Group, Post as Page, Comment as Note, Like/Dislike voting, Announce relay pattern, ChatMessage

Background knowledge about how group/forum federation works on the Fediverse using FEP-1b12 (FINAL status). Covers the Group actor type, the audience property for group identification, the Announce wrapping mechanism for content distribution, thread/comment structure (Page for top-level posts, Note for replies, inReplyTo chains), group moderation via attributedTo collection with Add/Remove activit

Background knowledge about how JSON-LD works on the Fediverse and in ActivityPub, including the difference between @id and id, @type and type (keyword aliasing via @context), the many forms a value can take (string, object with @value, object with @id, array, language-tagged value), the four JSON-LD document forms (compacted, expanded, flattened, framed), how @context works and when it is optional

Background knowledge about how long-form text works on the Fediverse and in ActivityPub, based on FEP-b2b8. Covers the Article type and when to use it instead of Note, the full set of Article properties (name, summary, content, preview, url, image, attributedTo, sensitive, etc.), the allowed HTML subset for content, the preview mechanism for microblogging client fallback, summary generation guidan

Background knowledge about reverse WebFinger discovery — finding a WebFinger address from an ActivityPub actor — based on FEP-2c59 (DRAFT status). Covers the `webfinger` property on actors, the forward vs reverse discovery problem, why `preferredUsername` is insufficient for reverse lookups, domain mismatch use cases, validation requirements (no-redirect string comparison), security considerations

Background knowledge about the OpenWebAuth (OWA) federated remote authentication protocol, based on FEP-61cf (DRAFT status). Covers the 5-step authentication handshake between home instance, target instance, and user browser; WebFinger discovery of redirect and token endpoints (rel="http://purl.org/openwebauth/v1" and v1#redirect); HTTP Signature signed token requests; RSA PKCS#1 v1.5 encrypted si

Background knowledge about Misskey, the Japanese-origin federated microblogging platform (created 2014 by syuilo). Covers Misskey's ActivityPub extensions (custom namespace https://misskey-hub.net/ns# with _misskey_content, _misskey_quote, _misskey_reaction for emoji reactions on Like activities, _misskey_votes, _misskey_talk for chat, isCat boolean, _misskey_followedMessage, _misskey_requireSigni

Background knowledge about FEP-67ff FEDERATION.md, the convention for documenting federation behavior in Fediverse projects. Covers the specification requirements (valid Markdown, repository root location), suggested template sections (protocols, FEPs, ActivityPub details), machine-readable discovery via NodeInfo 2.1 software.repository, the companion FEP-c893 (DOAP JSON-LD for automated capabilit

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-ke

Background knowledge about capability and extension discovery via NodeInfo in the Fediverse. Covers FEP-6481 (WITHDRAWN — specifying ActivityPub extension support with NodeInfo metadata.activitypub.extensions IRI arrays), its successor FEP-9fde (reverse-FQDN operations map with semver versioning), and the broader capability discovery landscape including FEP-eb22 (supported ActivityStreams types),

Background knowledge about Loops, the federated short-form video sharing platform (TikTok/Vine alternative for the Fediverse). Covers the key federation design decision of using Note objects with video attachments instead of Video objects for maximum cross-platform compatibility, the instance actor and shared inbox implementation, HTTP Signatures with SHA-256 digests, WebFinger discovery, the grap

Background knowledge about NodeBB, the modern open-source forum software built on Node.js with native ActivityPub federation (core feature since v4.0.0, January 2025). Covers the three actor types (Person user at /u/username, Group category at /category/<cid> implementing FEP-1b12 Group Federation with Announce relay pattern, Application instance actor), the two-level content hierarchy (category a