ATProto to Fediverse Bridge

A single-user bridge service that automatically cross-posts from your Bluesky account to your Mastodon account. Built specifically for Val.town with TypeScript and Deno.

• Connects your accounts: Securely links your Bluesky and Mastodon accounts using OAuth
• Automatic syncing: Checks for new Bluesky posts every 15 minutes and cross-posts them to Mastodon
• Smart filtering: Only syncs regular posts, not replies, reposts, or posts that start with mentions, so hopefully only content that makes sense in the Mastodon context
• Smart transformations: Converts Bluesky mentions (@handle.bsky.social) to profile links since they don't exist on Mastodon
• Media support: Uploads images and videos from Bluesky to your Mastodon instance
• Duplicate prevention: Tracks synced posts to avoid posting the same content twice
• Error handling: Retries failed posts and logs errors for troubleshooting

✅ OAuth authentication for both Bluesky and Mastodon
✅ Media cross-posting (images & videos)
✅ Mention transformation (handles → profile links)
✅ Duplicate prevention via content hashing
✅ Retry mechanism with exponential backoff
✅ Error logging and sync tracking
✅ Setup wizard for easy configuration

Just clone my https://www.val.town/x/tijs/atproto-to-fediverse val

HTTP Trigger (for the web interface and API):

• Set backend/index.ts as an HTTP val
• This serves the setup wizard and handles OAuth callbacks

Cron Trigger (for automatic syncing):

• Set cronjob.ts as a Cron val
• Schedule: */15 * * * * (every 15 minutes)
• For paid accounts, you can use shorter intervals like */5 * * * * (every 5 minutes)

Set these environment variables in your Val.town account:

# Your Val.town deployment URL
VALTOWN_URL=https://your-val-url.web.val.run

# Bluesky App Password for sync service (services do not work with oauth yet on bsky)
ATPROTO_APP_PASSWORD=your-bluesky-app-password

# Security: restrict login to specific handle only
ATPROTO_ALLOWED_HANDLE=your.handle.bsky.social

1. Go to Bluesky Settings > App Passwords
2. Create a new App Password (name it something like "Bridge Service")
3. Copy the generated password and set it as ATPROTO_APP_PASSWORD

The ATPROTO_ALLOWED_HANDLE variable restricts OAuth setup to only your Bluesky handle, preventing others from hijacking your single-user bridge service.

The OAuth client metadata is automatically generated based on your VALTOWN_URL environment variable. No manual configuration is needed!

The client metadata will be available at:

• https://your-val-url.web.val.run/client

The service automatically registers with your Mastodon instance during setup - no manual configuration needed.

1. Visit your HTTP val URL (e.g., https://your-val-url.web.val.run)
2. Check the Setup Status: The landing page shows a checklist of what environment variables need to be configured
3. Configure missing variables: Set any missing environment variables in your Val.town settings
4. Click "Get Started" to begin the setup wizard once all required variables are set
5. Connect your Bluesky account by entering your handle
6. Connect your Mastodon account by entering your instance URL
7. Complete the setup - that's all!

Once configured, the service runs automatically:

1. Every 15 minutes (or your configured interval), the cron job runs
2. It fetches new posts from your Bluesky account
3. Transforms the content (mentions become profile links)
4. Uploads any media to your Mastodon instance
5. Creates the cross-post on Mastodon
6. Logs the result for your review

✅ Included:

• Regular posts with text
• Posts with images/videos
• Posts with links and hashtags
• Posts with mentions (converted to profile links)

❌ Excluded:

• Replies to other posts
• Posts that start with mentions (e.g., "@handle.bsky.social blah blah") - these are typically conversation starters
• Empty posts
• Posts you've already cross-posted
• Re-posts (posts that embed another post)

• Connection Status: See which accounts are connected
• Sync Controls: Enable/disable auto-sync and trigger manual syncs
• Recent Activity: View recently synced posts and their status
• Error Logs: Track sync failures and troubleshoot issues
• Disconnect Options: Disconnect individual accounts if needed

Visit your val's dashboard to see:

• Setup status and account connections
• Recent sync activity and statistics
• Error logs for troubleshooting
• Post sync history

• Free Val.town accounts: 15-minute minimum sync interval
• Bluesky media limits: 1MB images, 100MB videos
• Mastodon compatibility: Works with all Mastodon instances
• Single user: Designed for personal use (one Bluesky → one Mastodon)

Setup issues: Check the setup status checklist on the landing page for missing environment variables
OAuth failures: Ensure your VALTOWN_URL is publicly accessible (client metadata is auto-generated at /client)
"Unauthorized" errors: Verify ATPROTO_ALLOWED_HANDLE matches your exact Bluesky handle
App Password errors: Generate a new App Password in Bluesky settings and update ATPROTO_APP_PASSWORD
Sync not working: Verify both accounts are connected in the dashboard
Missing posts: Check the sync logs for specific error messages
Media upload fails: Bluesky/Mastodon may have different file size limits

• All tokens are stored securely in SQLite
• No data leaves your Val.town instance
• OAuth follows security best practices (PKCE, DPoP)
• Single-user security: ATPROTO_ALLOWED_HANDLE restricts access to your handle only
• App Password option: More reliable than OAuth tokens for automated services
• You can disconnect accounts anytime from the dashboard
• Single-user architecture prevents data mixing

This is an open-source project. For issues or feature requests, check the repository or Val.town community forums.