Mastodon is a decentralized social network that works similarly to Twitter/X in function but fundamentally differently in structure. Instead of one company controlling everything, Mastodon consists of thousands of independent servers that communicate with each other.
Key Concepts
Instances (Servers)
An instance is an independent installation of Mastodon software. Each instance:
- Has its own domain (like mastodon.social or fosstodon.org)
- Is run by its own administrators
- Has its own rules and community culture
- Stores its users’ data
When you join Mastodon, you join a specific instance. But here’s the key insight: you can interact with people on other instances. Your mastodon.social account can follow, reply to, and interact with someone on fosstodon.org seamlessly.
Think of instances like email providers. You can have a Gmail address and email someone with an Outlook address. The underlying technology connects different providers transparently.
Federation
Federation is the technology that connects instances. When you follow someone on another instance:
- Your instance contacts their instance
- The instances establish a connection
- New posts flow automatically between servers
- You see their content in your timeline
This happens transparently—you don’t need to think about which instance someone is on during normal use.
Handles
Mastodon handles look like email addresses: @username@instance.domain
For example: @user@mastodon.social
The full handle uniquely identifies someone across the entire fediverse. Within your instance, you can often use just @username for local users.
Posts (Toots)
Mastodon posts were originally called “toots” (a playful reference to elephant sounds—the Mastodon mascot is a mammoth). Posts can include:
- Up to 500 characters (varies by instance)
- Images, videos, and audio
- Content warnings
- Visibility settings
- Polls
Boosts and Favorites
- Boost: Share someone’s post to your followers (like retweet)
- Favorite: Show appreciation (like a like)
Boosts propagate posts across instances. When you boost something, your followers see it even if they don’t follow the original poster.
Content Warnings
Content warnings (CWs) hide post content behind a label you provide. Readers click to reveal the content. Common uses:
- Spoilers for media
- Potentially sensitive topics
- Politics (on some instances)
- Long posts
- Eye contact in photos (in some communities)
CW norms vary significantly by instance and community.
Getting Started
1. Choose an Instance
This is often the hardest step for newcomers. Consider:
- Topic focus: Some instances center on specific interests (tech, art, gaming, academia)
- Size: Large instances have more content; small instances have tighter communities
- Rules: Read the instance rules—you’ll need to follow them
- Admin reputation: Who runs it? Are they responsive and trustworthy?
- Location: Some instances focus on specific regions or languages
You can always move later. Mastodon supports account migration.
2. Set Up Your Profile
Complete profiles get more follows:
- Clear display name
- Bio explaining who you are or what you post about
- Profile picture
- Header image (optional)
- Relevant hashtags in your bio
3. Make an Introduction Post
Many instances have an #introduction hashtag. Write a post about yourself:
- Who you are
- What you’re interested in
- What you might post about
- Relevant hashtags for your interests
This helps people find you and gives them reason to follow.
4. Follow People
Start building your timeline:
- Use the Local timeline to find people on your instance
- Search hashtags for your interests
- Check who interesting accounts follow
- Use discovery tools (see our tools guide)
5. Engage Thoughtfully
- Reply to posts
- Boost content you appreciate
- Use content warnings appropriately for your instance
- Be patient—building a network takes time
Timeline Types
Home Timeline
Posts from accounts you follow. This is your primary, curated experience.
Local Timeline
Public posts from everyone on your instance. Good for community engagement and discovery.
Federated Timeline
Public posts from all instances your server knows about. This is a firehose—useful for discovery but often overwhelming.
Lists
Custom timelines you create by grouping accounts. Powerful for organizing by topic or relationship.
Common Mistakes
Treating it like Twitter: The culture is different. Take time to observe norms before posting heavily.
Ignoring instance rules: Rules vary and matter. Read them.
Skipping content warnings: CWs are a valued community feature. Learn the norms.
Not filling out your profile: Empty profiles rarely get follows.
Only cross-posting: People can tell when you’re just mirroring from Twitter. Original presence works better.
Over-relying on the federated timeline: It’s a discovery tool, not your main feed.
Federation in Practice
What You See
You see content from:
- People you follow (Home)
- Your instance (Local)
- Instances your server knows about (Federated)
You might NOT see:
- Posts from instances your admin has blocked
- Posts from instances nobody on your server follows
- Very recent posts from distant instances (federation lag)
Incomplete Information
Because federation is distributed, you sometimes see:
- Incomplete reply threads
- Missing old posts from newly-discovered accounts
- Different favorite/boost counts than the original instance shows
This is normal. The trade-off for decentralization is some inconsistency.
Privacy and Visibility
Post Visibility Settings
- Public: Visible everywhere, appears in public timelines
- Unlisted: Visible to anyone with the link, but not in public timelines
- Followers-only: Only your followers can see it
- Direct: Only mentioned users can see it (NOT end-to-end encrypted)
Important Privacy Notes
- Your public posts are public—they can be indexed, shared, and seen by anyone
- Instance admins can technically access all content on their server
- Direct messages are not encrypted—treat them like email
- Deleted posts may persist in other servers’ caches
Learning More
To understand the broader ecosystem Mastodon is part of, see What is the Fediverse?.
For technical details on how federation works, see How Algorithmic Timelines Work and Developer Notes.
For tools to improve your experience, see Best Tools for Mastodon.
Frequently Asked Questions
Mastodon itself is free, open-source software. Most instances are free to join, though some may ask for donations to cover hosting costs.
Yes. Mastodon supports account migration—you can move your followers to a new instance. Your posts don't transfer, but your social connections do.
You lose access to that account. This is why choosing a stable instance matters and why some people self-host. You can export your follow list and other data as a backup.
Your instance only knows about replies that have been fetched—typically from users someone on your instance follows. This is a natural consequence of federation.
Mastodon timelines are chronological by default. Some clients offer optional algorithmic sorting. See How Algorithmic Timelines Work for context.
External Resources
For more foundational information, the Mastodon Wikipedia article provides historical context and technical background.