Mostr
Nostr-Fediverse bridge. Follow Mastodon users from Nostr and vice versa.
Overview
Mostr bridges the Nostr protocol with ActivityPub, enabling cross-platform communication between Nostr clients and Fediverse servers like Mastodon. It translates posts bidirectionally, allowing users to follow and interact across protocol boundaries.
Key Features
Bidirectional Bridge
┌─────────────────────────────────────────────────────────────────┐
│ Mostr Bridge │
├─────────────────────────────────────────────────────────────────┤
│ │
│ Nostr Mostr Fediverse │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ Client │◄──────────►│ Bridge │◄──────────►│ Mastodon │ │
│ │ (Damus) │ │ │ │ Server │ │
│ └──────────┘ └──────────┘ └──────────┘ │
│ │ │
│ │ │
│ Nostr events ◄──────────────► ActivityPub objects │
│ │
└─────────────────────────────────────────────────────────────────┘
Cross-Protocol Features
| Action | Nostr → Fediverse | Fediverse → Nostr |
|---|---|---|
| Follow | Follow Mastodon users | Follow Nostr users |
| Posts | Notes become toots | Toots become notes |
| Replies | Reply to Fediverse posts | Reply to Nostr posts |
| Reactions | Likes bridge | Likes bridge |
| Reposts | Boosts bridge | Reposts bridge |
How It Works
From Nostr:
Follow: @user@mastodon.social_at_mostr.pub
This translates to:
Nostr client → Mostr relay → ActivityPub federation → Mastodon
From Fediverse:
Follow: @npub1...@mostr.pub
Mastodon server → Mostr ActivityPub inbox → Nostr relay
Technical Architecture
Mostr operates as both:
- A Nostr relay (accepts/publishes events)
- An ActivityPub server (federates with Fediverse)
┌─────────────────────────────────────────────────────────────────┐
│ Mostr Architecture │
├─────────────────────────────────────────────────────────────────┤
│ │
│ ┌──────────────┐ ┌──────────────┐ │
│ │ Nostr Relay │ │ ActivityPub │ │
│ │ Interface │ │ Server │ │
│ └──────┬───────┘ └──────┬───────┘ │
│ │ │ │
│ │ ┌──────────────┐ │ │
│ └─────────►│ Translator │◄──────────┘ │
│ │ │ │
│ │ Event ↔ Object│ │
│ └──────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────┘
Usage
Following Fediverse from Nostr
- Find a Fediverse user:
@alice@mastodon.social - Convert to Mostr format:
alice@mastodon.social_at_mostr.pub - Follow in your Nostr client
Following Nostr from Fediverse
- Get your npub:
npub1abc123... - Fediverse users follow:
@npub1abc123...@mostr.pub
Limitations
- Not all post types translate perfectly
- Some Fediverse features (polls, etc.) may not bridge
- Relies on Mostr infrastructure
Comparison
| Feature | Mostr | Bridgy Fed | Direct |
|---|---|---|---|
| Nostr-ActivityPub | Yes | No | N/A |
| IndieWeb-ActivityPub | No | Yes | N/A |
| Nostr-Bluesky | Partial | Yes | N/A |
| Self-hostable | Limited | Yes | N/A |
Links
- Website: mostr.pub
- By: Soapbox
See Also
- Nostr Protocol — The protocol
- ActivityPub — Fediverse protocol
- Mastodon — Fediverse server