# Mastodon
Mastodon is a free, [[Open Source]] decentralized social network created by [[Eugen Rochko]] in 2016. Unlike centralized platforms like Twitter/X, Mastodon consists of thousands of independently operated servers (instances) that communicate via the [[ActivityPub]] protocol, forming part of the [[Fediverse]]. Users can choose an instance aligned with their interests or values, or run their own.
Rochko developed Mastodon as an alternative to corporate social media, emphasizing user control, privacy, and community moderation. The platform gained significant attention during Twitter's ownership changes in 2022, growing from ~300,000 to over 2.5 million active users. Mastodon is licensed under [[AGPL License]] and funded through Patreon and the non-profit Mastodon gGmbH based in Germany.
## Key Features
| Feature | Description |
|---------|-------------|
| **Toots/Posts** | Up to 500 characters (configurable per instance) |
| **Content Warnings** | Hide sensitive content behind warnings |
| **No Algorithm** | Chronological timeline, no engagement manipulation |
| **Federation** | Follow users across different instances |
| **Instance Rules** | Each server sets its own moderation policies |
| **No Ads** | No advertising or user data monetization |
| **Verified Links** | Verify identity via website rel="me" links |
## How Federation Works
```
┌─────────────────┐ ActivityPub ┌─────────────────┐
│ mastodon.social│◄──────────────────►│ fosstodon.org │
│ (Instance A) │ │ (Instance B) │
└────────┬────────┘ └────────┬────────┘
│ │
┌────┴────┐ ┌────┴────┐
│ User @a │ can follow and interact with│ User @b │
└─────────┘ └─────────┘
```
- Users have addresses like `@
[email protected]`
- Posts federate to followers' instances
- Instances can block other instances (defederation)
- Local timeline shows instance posts; federated shows all followed
## Mastodon vs Twitter/X
| Aspect | Mastodon | Twitter/X |
|--------|----------|-----------|
| Ownership | Decentralized/community | Corporate |
| Algorithm | None (chronological) | Engagement-based |
| Character limit | 500+ (configurable) | 280 (premium: more) |
| Ads | None | Yes |
| Data collection | Minimal | Extensive |
| Moderation | Per-instance | Centralized |
| Open source | Yes (AGPL) | No |
## Popular Instances
- **mastodon.social** - Flagship instance run by Mastodon gGmbH
- **fosstodon.org** - Free/open source software community
- **hachyderm.io** - Tech professionals
- **infosec.exchange** - Security community
- **mastodon.art** - Artists and creators
## Technical Stack
- **Backend**: Ruby on Rails
- **Frontend**: React.js
- **Database**: PostgreSQL
- **Search**: Elasticsearch (optional)
- **Protocol**: ActivityPub (W3C standard)
- **Streaming**: Node.js
## References
- https://joinmastodon.org
- https://github.com/mastodon/mastodon
- https://en.wikipedia.org/wiki/Mastodon_(social_network)
- https://docs.joinmastodon.org
## Related
- [[Eugen Rochko]]
- [[Fediverse]]
- [[ActivityPub]]
- [[Open Source]]
- [[AGPL License]]
- [[Decentralized Systems]]
- [[Social Media]]