Core concepts

Instance

An instance is one installation of Omicron running at one domain. It has its own accounts, posts, settings, and moderation rules. There is no central server: your instance is the whole product, and other instances are peers.

The instance has a name (shown in the UI) and a public domain (used in links, email, share cards, and your fediverse identity). Both are set in the setup wizard and editable later in the admin panel.

Account, actor, and handle

A local account is a user on your instance. When federation is enabled, that account is also an ActivityPub actor — an addressable identity other servers can follow and deliver activities to.

Its handle is @username@your-domain. Someone on Mastodon can paste that into their search box and follow directly.

Federation

Federation is the exchange of ActivityPub activities between servers. Omicron ships it turned off: a fresh instance is a private, standalone blog. Turning it on binds your server’s identity to your domain, which is why the domain must be set first and the change applies on restart.

Activity	What it means here
Follow	Someone subscribes to one of your writers. Inbound follows are auto-accepted (unless the account requires approval).
Create(Article/Note)	A new post is delivered to your followers’ inboxes.
Like	A like on a post, counted in the writer dashboard.
Announce	A boost/repost.
Undo	Reverses a previous Follow, Like, or Announce.

See How federation works for the full picture.

Inbox and outbox

Every actor has an inbox (where other servers deliver activities addressed to them) and an outbox (their own public activity stream). Omicron also exposes a shared inbox at /inbox so a remote server delivering one post to fifty of your followers can send it once.

Outbound delivery goes through a queue, so a slow or down remote server never blocks a user’s request.

Posts, drafts, and comments

A post is an article: title, optional cover image, and rich body text edited in Tiptap with full Markdown support. Unpublished posts are drafts and are never federated or publicly readable.

Comments are replies. Local comments and federated replies land in the same place.

Standalone vs federated

	Standalone	Federated
FEDERATION_ENABLED	false (default)	true
Public domain	Optional	Required
HTTPS	Recommended	Required in practice
ActivityPub code paths	Not even loaded	Active
Reachable by Mastodon	No	Yes

The setup model

Omicron’s configuration philosophy: the web UI is the interface, not the file system.

1. Generated automatically — database password, session secret, TLS certificates. You never see or type them.
2. Set in the wizard or admin panel — instance name, domain, email, federation toggle, moderation, scraper shield. Stored in the database.
3. Environment variables — a fallback for the above, plus infrastructure-level knobs (ports, external database, rate limits). Every one is optional; web settings take precedence.

See Configuration and Environment variables.

Volumes and state

Nothing you care about lives inside a container image:

Volume	Holds
pgdata	All Postgres data — accounts, posts, follows
uploads	User-uploaded media
secrets	Generated database password and bootstrap session secret
state	App-managed state, e.g. a UI-rotated session secret
redis_data	Queued jobs and pending federation deliveries
caddy_data	Let’s Encrypt certificates

Rebuilding recreates containers, never volumes. See Backups and restore.