Lemmy

Lemmy is a community discussion and link aggregation platform similar to Reddit, designed for running topic-based communities with posts, comments, and moderation tools. It supports federation via ActivityPub, allowing separate Lemmy servers (and other Fediverse platforms) to interact while remaining independently managed.

Key Features

• ActivityPub federation between instances, including cross-instance communities and users
• Reddit-style content model: communities, posts (links/text), threaded comments, voting, sorting, and feeds
• Moderation tooling: community moderators, admin controls, reporting, bans, and content removal
• User and community management including roles/permissions and instance policies
• Multiple clients/frontends via API ecosystem (official and third-party web/mobile apps)
• Media handling via URL/link posts and integrations commonly deployed with reverse proxies and object storage

Use Cases

• Host a private or public community forum with familiar upvote/downvote dynamics
• Create a federated network of communities across multiple organizations or groups
• Replace centralized community platforms while keeping local control over policies and moderation

Limitations and Considerations

• Federation can introduce moderation complexity (remote content, defederation decisions, instance-level policies)
• Operationally requires a database and supporting services; upgrades should follow release notes to avoid breaking changes

Lemmy is well-suited for communities that want a modern discussion experience with federation and local autonomy. Its ActivityPub support and active ecosystem make it a practical choice for building interconnected forums without relying on a single centralized provider.