Nostr vs ActivityPub vs Bluesky: Complete Protocol Comparison

A comprehensive technical comparison of the three major decentralized social protocols. Learn the architecture, trade-offs, and which protocol fits your needs.

Executive Summary

The decentralized social landscape has three major protocols competing for adoption: Nostr (Notes and Other Stuff Transmitted by Relays), ActivityPub (the protocol powering Mastodon), and Bluesky’s AT Protocol. Each represents a fundamentally different approach to solving the same problem: how to create social networks without centralized control.

Who Should Use Which Protocol?

• Choose Nostr if censorship resistance is your top priority, you want true data ownership, or you’re part of the Bitcoin/cryptography community
• Choose ActivityPub/Mastodon if you want an established network with mature apps, strong community moderation, or need to run a server for your organization
• Choose Bluesky if you want a polished user experience, corporate backing for longevity, or are migrating from Twitter and want familiarity

Protocol Architecture

Understanding how each protocol works technically helps explain their different strengths and limitations.

Nostr: The Client-Relay Model

Nostr is elegantly simple: it’s just clients and relays.

┌─────────────┐         ┌─────────────┐         ┌─────────────┐
│   Client    │◄───────►│   Relay 1   │◄───────►│   Client    │
│   (You)     │         │  (Public)   │         │  (Friend)   │
└─────────────┘         └─────────────┘         └─────────────┘
       │                       │
       │                ┌─────────────┐
       └───────────────►│   Relay 2   │
                        │  (Private)  │
                        └─────────────┘

How It Works:

1. Your Identity: A cryptographic key pair (npub/nsec) generated locally on your device
2. Posting: You sign events with your private key and send them to relays of your choice
3. Reading: Your client queries multiple relays to fetch posts from people you follow
4. No Central Registry: Anyone can run a relay; no approval needed to join the network

Key Characteristics:

• Stateless: Relays don’t maintain user accounts or relationships
• Redundant: You can use 10+ relays simultaneously; if one censors you, others still have your data
• Simple Protocol: The entire protocol is ~2,000 lines of specification
• No Federation: Relays don’t talk to each other; clients aggregate from multiple sources

ActivityPub: The Federated Server Model

ActivityPub creates a federation of interconnected servers, like email but for social media.

┌─────────────────────────────────────────────────────────────┐
│                      FEDERATED NETWORK                       │
├─────────────┐    ┌─────────────┐    ┌─────────────────────┐ │
│  Server A   │◄──►│  Server B   │◄──►│     Server C        │ │
│ (mastodon. │    │ (fosstodon. │    │ (infosec.exchange)  │ │
│  social)    │    │  org)       │    │                     │ │
└──────┬──────┘    └──────┬──────┘    └──────────┬──────────┘ │
       │                  │                      │            │
       ▼                  ▼                      ▼            │
  ┌─────────┐        ┌─────────┐          ┌─────────┐         │
  │ Users   │        │ Users   │          │ Users   │         │
  │ @alice  │        │ @bob    │          │ @carol  │         │
  └─────────┘        └─────────┘          └─────────┘         │
└─────────────────────────────────────────────────────────────┘

How It Works:

1. Your Identity: Assigned by the server you join (e.g., @user@server.com)
2. Posting: Your server stores your posts and pushes them to followers’ servers
3. Federation: Servers communicate using ActivityPub protocol to share posts across the network
4. Instance Administration: Each server has admins who set rules and moderate content

Key Characteristics:

• Instance-Centric: Your server is your home; it stores your data and manages your identity
• Server-to-Server: Servers actively communicate and share content
• Moderated: Each server sets its own content policies and can block other servers
• Mature Ecosystem: 5+ years of development, established best practices

Bluesky AT Protocol: The Personal Data Store Model

Bluesky combines ideas from both approaches with a focus on user experience and corporate backing.

┌──────────────────────────────────────────────────────────────┐
│                    BLUESKY ARCHITECTURE                       │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│  ┌─────────────┐    ┌─────────────┐    ┌─────────────────┐  │
│  │  Client App │    │  Client App │    │   Client App    │  │
│  │  (Bluesky)  │    │  (Graysky)  │    │   (Other)       │  │
│  └──────┬──────┘    └──────┬──────┘    └────────┬────────┘  │
│         │                  │                     │           │
│         └──────────────────┼─────────────────────┘           │
│                            │                                 │
│         ┌──────────────────┼──────────────────┐              │
│         │                  ▼                  │              │
│         │         ┌─────────────┐             │              │
│         │         │  Relay      │             │              │
│         │         │  (Indexer)  │             │              │
│         │         └──────┬──────┘             │              │
│         │                │                    │              │
│         ▼                ▼                    ▼              │
│  ┌─────────────┐    ┌─────────────┐    ┌─────────────┐       │
│  │    PDS      │    │    PDS      │    │    PDS      │       │
│  │(alice.com)  │    │(bob.host)   │    │(carol.net)  │       │
│  └─────────────┘    └─────────────┘    └─────────────┘       │
│  Personal Data Stores                                        │
└──────────────────────────────────────────────────────────────┘

How It Works:

1. Your Identity: A Decentralized Identifier (DID) that can be linked to domain handles
2. Personal Data Store (PDS): Your data lives on a PDS—initially Bluesky-hosted, but can be self-hosted
3. Relay/Indexer: Bluesky runs relays that aggregate data from all PDSes and build search indexes
4. Client Independence: Any app can read from the relay network using your DID

Key Characteristics:

• Hybrid Approach: Combines user data ownership with centralized indexing
• Domain Handles: Your identity can be tied to domains you control (alice.com)
• Gradual Decentralization: Currently centralized, but designed to become more decentralized over time
• Commercial Backing: Bluesky PBC provides stability and resources for development

Key Differences

Identity and Authentication

Nostr takes the most radical approach: your identity is purely cryptographic. Lose your private key (nsec) and your identity is gone forever. This is a feature for censorship resistance—no authority can seize or reset your identity—but requires careful key management.

ActivityPub uses traditional server-based authentication. This is familiar (like email) and allows password resets, but creates lock-in: your identity is tied to your server. If mastodon.social bans you, you lose @yourname@mastodon.social.

Bluesky offers a middle ground: your core identity is a DID (decentralized identifier) that persists regardless of handle changes. You can move between PDS providers while keeping your identity, similar to porting a phone number between carriers.

Censorship Resistance

Nostr: Maximum Resistance

• No central authority can ban you from the protocol
• Anyone can run a relay; you only need one to participate
• Content is cryptographically signed—can’t be forged or modified
• If a relay blocks you, use a different one
• Trade-off: Spam is harder to prevent; moderation is client-side

ActivityPub: Moderated Federation

• Your server admin can ban you from their instance
• Servers can defederate (block) other servers entirely
• Creates “safe spaces” but also echo chambers
• Trade-off: Strong community moderation but potential for fragmentation

Bluesky: Corporate Moderation

• Bluesky PBC can moderate at the relay level
• Self-hosted PDSes provide some independence
• Domain-based verification creates reputation systems
• Trade-off: Better spam prevention, but relies on Bluesky’s goodwill

Scalability and Performance

Nostr:

• ✅ Horizontal scaling: more relays = more capacity
• ✅ No single point of failure
• ⚠️ Client must query multiple relays (bandwidth intensive)
• ⚠️ No global view; content discovery is hard
• ⚠️ Relay storage costs may limit history retention

ActivityPub:

• ✅ Efficient: servers only fetch what their users need
• ✅ Established scaling patterns (see Mastodon.social)
• ⚠️ Instance outages affect all their users
• ⚠️ “Federated timeline” doesn’t scale to millions of users

Bluesky:

• ✅ Centralized relay provides fast, consistent queries
• ✅ Professional infrastructure (CDN, caching, etc.)
• ⚠️ Currently centralized; true decentralization TBD
• ⚠️ Relay is a bottleneck and potential point of control

Data Portability

Nostr:

• ✅ Native portability: your data exists on multiple relays
• ✅ Switch clients instantly: just import your nsec
• ✅ No vendor lock-in by design
• ⚠️ No guarantee of data persistence (relays can drop old data)

ActivityPub:

• ⚠️ Data export depends on your server
• ⚠️ Moving servers = new identity
• ⚠️ Followers don’t transfer automatically (“account migration” is partial)
• ✅ Some servers offer good export tools

Bluesky:

• ✅ Designed for portability from the ground up
• ✅ All data accessible via API
• ✅ Account migration tools built-in
• ⚠️ Currently relies on Bluesky’s hosted PDS

Privacy Considerations

Nostr:

• ✅ No phone number or email required
• ✅ Pseudonymous by default
• ⚠️ All posts are public (encrypted DMs are optional)
• ⚠️ Metadata analysis possible (which relays you use, when you post)

ActivityPub:

• ⚠️ Server admins can read DMs
• ⚠️ Email usually required for registration
• ✅ Private posts possible (server-dependent)
• ✅ Some instances prioritize privacy

Bluesky:

• ⚠️ Phone verification increasingly required
• ⚠️ Bluesky PBC has access to data
• ⚠️ Real-name policy encouraged (domain handles)
• ✅ Privacy controls in the protocol

Developer Experience

Nostr:

• ✅ Extremely simple protocol (learn in a day)
• ✅ No server required to build a client
• ✅ Thriving open-source ecosystem
• ⚠️ Fragmented (many competing standards/NIPs)
• ⚠️ Limited built-in features (must implement everything)

ActivityPub:

• ✅ Mature libraries in many languages
• ✅ Well-documented W3C standard
• ✅ Existing implementations to study
• ⚠️ Complex protocol (ActivityStreams + ActivityPub)
• ⚠️ Server development required for most apps

Bluesky:

• ✅ Modern, well-designed APIs
• ✅ Strong TypeScript support
• ✅ Active developer community
• ⚠️ Protocol still evolving
• ⚠️ Currently dependent on Bluesky infrastructure

Use Case Recommendations

Choose Nostr If…

✅ Censorship resistance is non-negotiable

• You’re a journalist in an authoritarian country
• You discuss politically sensitive topics
• You’ve been banned from other platforms

✅ You value simplicity and ownership

• You want to truly own your identity
• You prefer minimal, Bitcoin-aligned technology
• You accept responsibility for key management

✅ You’re building in the Bitcoin ecosystem

• Lightning Network integration is important
• You want censorship-resistant value transfer
• You’re already familiar with key management

Best Clients: Damus (iOS), Amethyst (Android), Iris (Web), Primal (All platforms)

Choose ActivityPub/Mastodon If…

✅ You want an established, mature network

• You need reliable, well-tested software
• Community moderation is important to you
• You want to join existing communities (infosec, academics, artists)

✅ You’re running a community or organization

• You need server-level control
• You want to set community guidelines
• You need moderation tools for your group

✅ You prefer familiar social media patterns

• You like the Twitter-like interface
• You want private posts and granular privacy settings
• Server-based moderation appeals to you

Best Servers: mastodon.social (general), fosstodon.org (tech), infosec.exchange (security), hachyderm.io (tech)

Choose Bluesky If…

✅ You want a polished, mainstream experience

• You’re migrating from Twitter and want familiarity
• User experience is your top priority
• You want professional support and development

✅ You’re a content creator or public figure

• Domain verification matters to you
• You want algorithmic choice (multiple feeds)
• You need reliable infrastructure

✅ You trust corporate-backed decentralization

• You believe gradual decentralization is realistic
• You want VC-backed resources for growth
• You accept trade-offs for usability

Best Clients: Official Bluesky app, Graysky (mobile), Tokimeki (web)

Migration Guides

Moving from Twitter

All three protocols offer escape routes from Twitter/X, but the experience differs:

Twitter → Nostr:

1. Find your community: Nostr is still niche; search for your interests
2. Follow Twitter bridges: Some accounts mirror Twitter to Nostr
3. Cross-post initially: Use tools like NostrPad or manual copy-paste
4. Embrace the differences: No algorithms, no virality—just chronological feeds
5. Build slowly: Nostr rewards authentic engagement over follower counts

Twitter → ActivityPub/Mastodon:

1. Choose your server: Research instances aligned with your interests
2. Use migration tools: Twitter export → Mastodon import tools exist
3. Follow Twitter bridges: @TwitterBridge and similar services
4. Learn the culture: Content warnings, alt text, and federation etiquette
5. Bring your network: Many Twitter communities have Mastodon mirrors

Twitter → Bluesky:

1. Easiest transition: Interface is very similar to old Twitter
2. Find your people: Bluesky has the most Twitter migrants
3. Use domain verification: Claim your domain for credibility
4. Explore custom feeds: Bluesky’s algorithm marketplace replaces Twitter’s single feed
5. Cross-post easily: Most tools support Bluesky natively

Cross-Posting Strategies

The Bridge Approach:

• Use services like Nostr2Twitter, Mastodon-Twitter Crossposter, or Bluesky’s native tools
• Post to one platform, mirror to others
• Pro: Maximum reach | Con: Fragmented conversations

The Hub Approach:

• Choose one platform as your “home”
• Manually share best content to others
• Pro: Authentic engagement on each platform | Con: Time intensive

The Separation Approach:

• Different content for each platform
• Nostr: Uncensored thoughts, Bitcoin content
• ActivityPub: Community discussions, niche interests
• Bluesky: Professional presence, mainstream content
• Pro: Platform-appropriate content | Con: Harder to maintain

Migration Checklist

Before You Leave Twitter:

• Export your Twitter data (Settings → Your Account → Download an archive)
• Save important contacts and conversations
• Announce your move (pin a tweet with your new handles)
• Update your bio with new protocol links
• Set up cross-posting if desired

First Week on New Platform:

• Complete your profile (photo, bio, links)
• Follow 50-100 people to seed your timeline
• Post an introduction message
• Engage with others’ posts (reply, repost)
• Join relevant communities/hashtags

First Month:

• Establish posting rhythm
• Build initial follower base
• Learn platform-specific features
• Contribute value (don’t just promote)
• Evaluate if this is your new home

Future Outlook

Protocol Roadmaps

Nostr:

• NIP Development: Continuous improvement via Nostr Improvement Proposals
• Lightning Integration: Deeper Bitcoin/Lightning payment integration
• Private Messaging: Enhanced encrypted communications (NIP-17)
• Reputation Systems: Decentralized reputation without central authorities
• Relay Innovation: Paid relay models for sustainability

ActivityPub:

• Fediverse Futures: Groups, events, and richer interactions
• Improved Migration: Better account portability between instances
• Moderation Tools: Shared blocklists and collaborative filtering
• ActivityPub 2.0: Potential protocol evolution for better scaling

Bluesky:

• Self-Hosting: Personal Data Store (PDS) self-hosting launch
• Federation: Opening relay network to third parties
• Custom Algorithms: More sophisticated feed algorithms
• Verification: Decentralized identity verification systems

Interoperability Possibilities

The Bridge Reality:

• Nostr ↔ ActivityPub: Bridges exist but are imperfect
• Bluesky ↔ Others: Bluesky is currently isolated but planning bridges
• Cross-Protocol Identity: Unified identity across protocols remains hard

Technical Challenges:

• Different data models make seamless bridging difficult
• Moderation policies clash between protocols
• Spam prevention differs fundamentally

Potential Solutions:

• Dual-posting clients: Apps that post to multiple protocols simultaneously
• Unified identity layers: Services that map identities across protocols
• Read-only bridges: Consume content from other protocols without full interaction

Coexistence Scenarios

Likely Future: Complementary Ecosystems

Rather than one protocol “winning,” we’re likely to see:

1. Nostr remains the choice for censorship-resistant, Bitcoin-aligned communication
2. ActivityPub continues as the mature, community-focused federation
3. Bluesky becomes the mainstream, corporate-friendly option

Each serves different needs and values, similar to how:

• Email (federated) coexists with Signal (centralized but encrypted) and Matrix (decentralized)
• Different cryptocurrencies serve different use cases

What This Means for You:

You don’t have to choose just one. Many users maintain presence across all three:

• Nostr for uncensored Bitcoin discussion
• ActivityPub for niche communities and long-form content
• Bluesky for professional networking and mainstream reach

The future of social media is not a single platform—it’s a protocol-native world where users control their identities and data flows freely between networks.

Test Your Protocol Knowledge

Ready to see if you understand the key differences between protocols?

Last updated: February 2026 | Protocol versions: Nostr (NIPs current), ActivityPub (W3C Recommendation), AT Protocol (v1.0)

Have questions? Join the discussion on Nostr, Mastodon, or Bluesky.