Using Mostr Bridge to Follow Friends Across Mastodon, Nostr, and Beyond

The decentralized social web is fragmented across protocols. Your friends might be on Mastodon (ActivityPub), Nostr, or other networks. Mostr Bridge is one of the most interesting projects trying to connect these worlds. This guide explains how it works, what it can and cannot do, and how to use it effectively.

What You’ll Know by the End

What Mostr Bridge is and how it connects Mastodon and Nostr
The technical approach behind protocol bridging
Practical steps for using Mostr Bridge
Limitations and trade-offs of cross-protocol bridging
Privacy and consent considerations

What Mostr Bridge Does

Mostr Bridge connects two fundamentally different protocols:

ActivityPub (used by Mastodon, Pixelfed, Lemmy, and the rest of the fediverse)
Nostr (Notes and Other Stuff Transmitted by Relays)

The bridge creates proxy accounts that represent users from one protocol on the other. When a Nostr user posts, the bridge creates an ActivityPub representation of that post that Mastodon users can see and interact with, and vice versa.

How It Works Technically

Nostr → Mastodon: The bridge monitors Nostr relays for posts. When it sees a post, it creates an ActivityPub activity and delivers it to any Mastodon users who follow that Nostr user’s bridge account.
Mastodon → Nostr: When a Mastodon user posts, the bridge signs the content with a Nostr key and publishes it to Nostr relays.
Interactions: Replies, boosts, and likes are translated between protocols where possible. Not all interaction types have equivalents on both sides.

Setting Up Mostr Bridge

Following Nostr Users from Mastodon

Find the Nostr user’s public key (npub)
Search for their bridge handle from Mastodon (typically npub...@mostr.pub or similar)
Follow the bridge account
Their Nostr posts will appear in your Mastodon home timeline

Following Mastodon Users from Nostr

Find the bridge relay address for the Mostr Bridge
Add it to your Nostr client’s relay list
Search for the Mastodon user’s bridge identity
Follow them through your Nostr client

Bridging Your Own Account

If you want your Mastodon posts to appear on Nostr (or vice versa):

Create accounts on both platforms
Register with the Mostr Bridge service
Link your accounts through the bridge’s verification process
Configure which content you want bridged (public posts only, typically)

What Works Well

Basic post federation: Text posts translate between protocols reliably
Following: Cross-protocol following works for public content
Discovery: Finding friends on the other protocol is possible through the bridge
Low friction: You do not need to create a native account on the other protocol to see content

What Does Not Work (or Works Poorly)

Rich media: Image handling can be inconsistent across bridges
Threaded conversations: Reply threading may not display correctly on both sides
Platform-specific features: Nostr zaps, Mastodon content warnings, and protocol-specific interactions do not translate
Real-time updates: There can be delays in bridging content, especially during high-traffic periods
Identity verification: Verifying that a bridge account actually represents who it claims to requires checking the bridge’s verification system
Direct messages: Private messages should NOT be bridged between protocols for security reasons

Bridging raises important questions about consent:

Your content reaches places you may not expect: When bridged, your Mastodon post appears on Nostr relays, which have different data retention and privacy norms. Similarly, Nostr posts appearing on Mastodon instances are subject to those instances’ policies.

Opt-in vs. opt-out: The fediverse community has strong opinions about consent in bridging. Many users want explicit opt-in before their content is bridged to another protocol.

Metadata exposure: Bridging may expose metadata (timestamps, interaction patterns) across protocol boundaries in ways you did not anticipate.

Blocking and muting: Blocking a bridged account on Mastodon does not block the underlying Nostr account, and vice versa. The bridge handles block propagation imperfectly.

Only bridge your own content, not others’
Respect users who request not to be bridged
Be transparent about your bridging in your profile bio
Understand the privacy implications on both sides

The Broader Bridging Landscape

Mostr Bridge is not the only cross-protocol bridge:

Mastodon ↔ Bluesky bridges: Experimental bridges exist for connecting ActivityPub and AT Protocol, though they face similar limitations
ActivityPub ↔ Email bridges: Some projects bridge fediverse content to email newsletters
RSS bridges: Several tools can publish Mastodon feeds as RSS, making content accessible to RSS readers

Each bridge has different maturity levels, features, and trade-offs. The bridging ecosystem is evolving rapidly.

For more on cross-protocol considerations, see our developer notes.

When Bridging Makes Sense

Good use cases:

Following a small number of specific people on a different protocol
Publishing your content to a wider audience across networks
Testing a new protocol without fully committing to it
Maintaining presence on multiple networks with minimal effort

Poor use cases:

Expecting a seamless multi-protocol experience
Bridging private or sensitive content
Replacing native platform presence entirely with a bridge
High-volume, real-time interaction across protocols

Common Mistakes

Assuming bridging is transparent: Bridged content often loses formatting, media quality, or context
Bridging without checking consent norms: The fediverse community has strong feelings about consent in bridging; respect them
Relying on bridges for important communications: Bridges can go down or have delays; use native platform access for critical interactions
Not disclosing bridge use: Be transparent in your bio if your account is bridged
Expecting all features to work: Protocol-specific features do not translate; understand the limitations before relying on a bridge

Frequently Asked Questions

Is Mostr Bridge official? Mostr Bridge is a community project, not officially affiliated with Mastodon or Nostr. It operates independently.

Can I bridge my Mastodon account without anyone knowing? Technically yes, but transparency is a strong community norm. Disclosing bridge use in your bio is recommended.

Does bridging cost anything? Most bridges are free to use. They are typically funded by donations or the operators’ own resources.

What happens if the bridge goes down? Cross-protocol interactions stop until the bridge is restored. Your native accounts on each platform continue to work normally. Check our tools page for bridge status resources.

Can I bridge to multiple protocols at once? In theory, yes — you could bridge to Nostr and Bluesky simultaneously. In practice, each bridge is separate and must be configured independently.

Should I use a bridge or just create accounts on both platforms? For casual cross-protocol following, bridges are convenient. For active participation, native accounts give you a better experience. Many users use both. See our articles hub for platform comparison guides.