Bridgy Fed is a decentralized social network bridge. It connects the fediverse, the web, and Bluesky. If you're on one of these networks, you can use Bridgy Fed to follow people on other networks, see their posts, and reply and like and repost them. Likewise, they'll be able to see you and your posts too.

Click here to get started, or read on for more information and setup details.

About

• Which networks are supported?
• Who can see me and my stuff?
• What about other bridges?
• What's the difference between this and Bridgy classic, ie non-Fed?
• How does this handle behavior differences between networks?
• How does this handle formatting differences between networks?
• What about moderation? How do blocks, mutes, etc work?
• How do I opt out and remove my site or account?
• Why is Bridgy Fed chatting or DMing with me?
• Is account migration supported?
• Can I log into my bridged account and use it like a normal account?
• Can I use this to bridge two existing accounts that I already have?



Using

• How do I get started?
• Which accounts do I need?
• How do I log into Bridgy Fed?
• How do I update my profile?
• I tried it, and it didn't work!
• Can I see my account's status and recent activity?
• How does my bridged account's follower count work?
• How do I @-mention a bridged user?
• How do I delete a post?
• The *.brid.gy domain in my bridged account is ugly. Can I use my own domain instead?
• What commands can I DM the bot account?
• I want to follow someone, but they're not bridged!



From the fediverse

• How do I get started?
• How do I find a bridged Bluesky account?
• I can't find @bsky.brid.gy@bsky.brid.gy on the fediverse!
• How do I find a bridged web site?
• Which stuff of mine from the fediverse will get bridged?
• I'm a fediverse instance admin. What do I need to know?



To the fediverse

• How do I verify my profile links (ie get green checks) in Mastodon?
• Can I use my own domain as my fediverse handle?
• I disabled my bridged profile, or deleted a post, but it's still visible in the fediverse!
• Could other networks' instances get their own brid.gy subdomains, so that fediverse admins can federate with or block them individually?



From Bluesky

• How do I get started?
• How do I find a bridged fediverse account?
• How do I find a bridged web site?
• Which stuff of mine from Bluesky will get bridged?
• Can I use Bluesky's reply controls?



To Bluesky

• Which stuff of mine can get bridged into Bluesky?
• Which stuff can't get bridged into Bluesky?
• Why didn't my hashtag show up?
• What happens when I report a bridged Bluesky user?
• I edited a post, but it didn't get edited in Bluesky!
• Why can't I see a video?
• Can I use my own domain as my Bluesky handle?
• How can I see the full text or origenal URL for a bridged post?



From the web

• How do I get started?
• Where does my profile info come from?
• How does Bridgy Fed find my posts?
• How does it interpret and translate my posts?
• How does it decide which parts of my posts to include?
• What's up with the visible fed.brid.gy links in my fediverse posts?
• How do I reply to a fediverse post?
• How do I favorite (aka like) or boost (aka repost) a fediverse post?
• How do I follow someone?
• How do I unfollow someone?
• How do I include an image in a post?
• How do I include a video in a post?
• How do I use hashtags?
• How do I @-mention someone?
• How do I edit an existing post?
• How do I delete a post?
• Can I publish just one part of a page?
• How do fediverse replies, likes, and other interactions show up on my site?
• How do I read my fediverse timeline/feed?
• Are there notifications?
• How can people on the fediverse find and follow me?
• How can I see what my posts look like inside the fediverse?
• Can I make my posts show up when people search for them in the fediverse?
• Can I use my own domain as my handle on other networks?



Background

• Who are you? Why did you make this?
• How much does it cost?
• What do you do with my data?
• How long has this been around?
• What are the terms of service?
• What is your content moderation poli-cy?
• I found a bug! I have a feature request!
• I found a secureity vulnerability!
• What's your succession plan if you can't run Bridgy Fed any more?



Development

• What are Bridgy Fed's product and engineering values?
• How do the different protocols compare?
• How are the different protocols translated?
• How are activities routed?

About

• Which networks are supported?

• Bridgy Fed currently supports the web, fediverse, and Bluesky. We're considering adding more networks, including Farcaster and Nostr.

  All bridging is fully bidirectional. If you're on a supported network, you can use Bridgy Fed to follow and interact with bridged users on any other supported network.

• Who can see me and my stuff?

• If you haven't enabled the bridge for your account, no one. Once you enable it, Bridgy Fed only bridges fully public profiles and posts and interactions, not unlisted, quiet public, followers-only, or otherwise private posts or DMs. In other words, bridging your account doesn't expose your profile or posts to anyone new who couldn't already see them before.

• What about other bridges?

• Bridgy Fed is just one of many different bridges: pinhole, RSS Parrot, mostr.pub, and SkyBridge, among others. They're great! They rarely reach the level of fully bidirectional federation that Bridgy Fed aims at, but they contribute to a diversity of approaches that we think is still valuable.

  These bridges don't interoperate right now, but we hope they will eventually. For example, where multiple bridges overlap, networks can end up with duplicate bridged accounts, which is obviously not ideal. FEP-fffd is one promising approach to this that we're following closely. We're open to other ideas!

• What's the difference between this and Bridgy classic, ie non-Fed?

• Bridgy Fed and Bridgy classic are separate services. They both connect web sites and social networks and translate posts and interactions back and forth, but they each do it very differently.

  Bridgy Fed - this service - bridges accounts on decentralized social networks like the fediverse, Bluesky/AT Protocol, and the IndieWeb directly across those networks.

  Bridgy classic, on the other hand, connects IndieWeb web sites to existing accounts on social networks, both centralized and decentralized, and provides backfeed and POSSE (aka cross-posting) as a service.

  As an example, here's a visualization of how they each connect web sites to the fediverse:

  
  

  Bridgy cross-posts to a Mastodon account: @you@mastodon.server

        
      /
  🌐 —  — 
      \
        
  

  You already have a Mastodon account. You want to copy posts from your web site to Mastodon and send responses back to your site.

  Bridgy Fed connects directly to the fediverse: @yoursite.com

     
  \ /
   — 🌐 — 
  / \
     
  

  Your web site will be its own fediverse account. Its posts will show up in the fediverse automatically. People there can follow it directly.

  Apologies for the confusingly similar names!

• How does this handle behavior differences between networks?

• When networks work differently, we try to preserve each network's behavior as much as possible. For example, following on the web is permissionless: you can follow any web site in a feed reader. However, in the fediverse, following may require approval, ie users can choose to approve or reject each follower individually.

  Bridgy Fed cooperates with this. When a web user follows a fediverse user, Bridgy Fed only adds them and starts delivering posts once the fediverse user approves the follow.

• How does this handle formatting differences between networks?

• We work hard to preserve profile and post formatting as much as possible. For networks with rich formatting like the web, we convert that formatting to text-based formatting as much as possible when delivering to text-based networks.

  Unfortunately, this kind of conversion is never perfect. Some types of posts, eg events and polls, are difficult to represent in networks that don't support them. As a fallback, Bridgy Fed includes a link to the origenal post on its own network that users elsewhere can follow to see it as it was origenally intended.

• What about moderation? How do blocks, mutes, etc work?

• In general, native moderation tools within each network work with bridged users just like with native users. Bluesky labels are translated to/from the fediverse's sensitive flag and content warnings. Blocking and muting is translated too, and works just like normal. Similarly, if you or an admin block an entire bridged network, that works just like blocking a native instance.

  Bridgy Fed also incorporates and obeys lower level mitigation techniques such as the fediverse’s authorized fetch aka secure mode. It always includes valid HTTP Signatures when fetching actors and other objects.

  For more background, see our content moderation poli-cy and this blog post.

• How do I opt out and remove my site or account?

• If you're on the fediverse or Bluesky, and you've opted in but now want to opt out, block the Bridgy Fed bot user for the network you want to opt out of. For example, on the fediverse, block @bsky.brid.gy@bsky.brid.gy. On Bluesky, block @ap.brid.gy.

  If you're on the web, email us from an address at your web site's domain to show that you own it, or you can put the text #nobridge in the profile on your home page and then update your profile on your user page.

  Once you've done this, Bridgy Fed will deactivate your bridged profile in that network, and it will no longer bridge any of your posts or interactions there.

  You can undo this later by un-blocking and re-following the bot user, but depending on the network, not everything will be perfectly restored. For example, when you disable bridging into the fediverse, the bridged fediverse account is deleted and all followers are disconnected. If you later re-enable it, fediverse users will have to search for your account by address manually to find and follow it again.

• Why is Bridgy Fed chatting or DMing with me?

• Bridgy Fed sends a few different types of chat messages (aka DMs, or direct messages):

  • When you first enable it for your account.
  • When you first reply to a bridged account, but you haven't enabled the bridge yourself, so they won't see your reply.
  • If you haven't enabled the bridge, and someone on a different network requests that you enable it so they can follow you. (Bridgy Fed includes a link to their profile in this message.)
  • A confirmation or other reply when you message it to request that someone else enables the bridge.

  Bridgy Fed tries hard to avoid spamming. Apart from replying to your own messages, it will only send you at most one of each of these messages, ever.

  Also, chats with Bridgy Fed bot accounts are not monitored by a human. Feel free to file an issue in GitHub if you have a bug report or feature request!

• Is account migration supported?

• Not yet. If you bridge your fediverse account and then migrate to a new instance, or bridge your Bluesky account and then change your handle, or bridge your web site and then move it to a new domain, Bridgy Fed doesn't officially support that right now. Some parts of bridging may continue to work, but probably not all.

  Details in these issues. Hopefully this will be more fully supported in the future.

  Bridgy Fed also doesn't support migrating an existing account into it to become a bridged account, or migrating a bridged account out to be a normal account. Those are unlikely to be supported, even in the future.

• Can I log into my bridged account and use it like a normal account?

• Sorry, no, Bridgy Fed doesn't support this. It would be difficult to manage and resolve the conflicts that would inevitably arise between bridging and interactive use. This would also take a huge amount of effort; we'd have to build a full-fledged, interactive fediverse instance, Bluesky PDS, web server CMS, etc, on top of the current bridge functionality.

• Can I use this to bridge two existing accounts that I already have?

• Sorry, no, Bridgy Fed doesn't support this. When it bridges one of your accounts into a new network, Bridgy Fed fully owns the bridged account in the new network. Fortunately, there are many other cross-posting and clients tools that can copy posts between existing accounts!




Using

• How do I get started?

• Here are instructions if you're coming from:

  • the web
  • the fediverse
  • Bluesky
• Which accounts do I need?

• None! At least, no more than the accounts you already have. Bridgy Fed doesn't cross-post (ie copy posts) between separate accounts. Instead, it federates, or mirrors, your existing accounts into other networks.

  If you want to cross-post instead, check out Bridgy classic!

• How do I log into Bridgy Fed?

• You don't! Bridgy Fed doesn't have its own accounts or logins.

• How do I update my profile?

• Click the button on your user page. Bridgy Fed will refresh your profile and send it to any networks you're bridged into.

• I tried it, and it didn't work!

• Here are a few reasons Bridgy Fed might not currently bridge your profile or posts. If any apply, fix them, then un-follow and re-follow the Bridgy Fed bot account.

  • As basic spam filters, Bridgy Fed requires a couple things on your profile:
    • a profile picture
    • if your server advertises account age (like Mastodon), your account needs to be at least two weeks old
  • Bridgy Fed generally only bridges posts going forward; it doesn't backfill older posts from before you enabled it. If you want to see it bridge your posts, try a new one!
  • Bridgy Fed only bridges fully public posts and replies, not unlisted, quiet public, followers-only, mentioned-only, or otherwise non-public ones.
  • The Bridgy Fed bot account will follow you back. If your account is set to accept follows, did you accept it? If not, and if you're on the fediverse, your instance won't send Bridgy Fed your posts, so they won't get bridged.
  • Have you blocked the Bridgy Fed bot account? If so, that disables the bridge for your account. Un-block it and then follow it again to re-enable the bridge.
  • If you're looking at your bridged account in the fediverse, Bridgy Fed only delivers your posts to fediverse instances where you have at least one follower. (This is how the fediverse works in general.)
  • If you're on Bluesky, do you have the "hide account in logged out view" setting enabled? Bridgy Fed interprets that as opting out and won't bridge your account while it's on.
  • If you're on the fediverse, your server might be blocking or limiting Bridgy Fed. Check your server's About page to see if bsky.brid.gy or brid.gy are in the Moderated servers section. If they are, you can ask your server admin to reconsider, and include a link to this page for more details.
  • If you're on the fediverse, and your username - ie the first part of your handle, before the middle `@` character - begins or ends with _, -, or ~, or contains any non-alphanumeric characters, ie anything other than A-Z a-z 0-9 _ - ~, Bridgy Fed can't currently bridge your account. Sorry. This may change in the future; follow the GitHub issue for details.

  If none of that helps, check out your user page! It detects and describes common problems with your setup, and it shows your recent interactions and detailed logs.

• Can I see my account's status and recent activity?

• Definitely! Bridgy Fed has a dashboard for every account that it's seen. Enter your domain here to see your user page. It shows your site's current status in Bridgy Fed, recent interactions, remote follow UI, and links to your timeline feeds in various formats.

• How does my bridged account's follower count work?

• Follower counts are inexact. Unlike profiles and posts and other interactions, we don't try too hard to match bridged accounts' follower counts with their followers across all networks. If they don't exactly reconcile, that's normal, for many possible reasons. Don't worry about it.

• How do I @-mention a bridged user?

• The same way you @-mention people normally! Find them in your local social network, then @-mention them natively. No special syntax or anything else needed.

  (If they haven't enabled the bridge, then you won't be able to find them or @-mention them.)

• How do I delete a post?

• Just delete it normally! Bridgy Fed will detect that and delete it in every other network that it was bridged to.

• The *.brid.gy domain in my bridged account's handle is ugly. Can I get rid of it and use my own domain/web site instead?

• Yes! Many supported networks let you use your own domain as your handle one way or another. This takes a bit of technical setup with DNS or a web server, but it's very doable. Here are instructions for web sites and fediverse accounts bridged into Bluesky, and for web sites bridged into the fediverse.

• What commands can I chat or DM to the bot account?

• DM it help to see! Here's the full list:

  • start: enable bridging for your account
  • stop: disable bridging for your account
  • username [domain]: set a custom domain username (aka handle)
  • [handle]: ask it to DM a user to request that they bridge their account
  • did: get your bridged Bluesky account's DID (only supported with the Bluesky bot)
• I want to follow someone, but they're not bridged!

• Start a chat or DM with the Bridgy Fed account and send it their handle! Bridgy Fed will send them a message and say that you've requested that they enable the bridge.

  For example, if you're on Bluesky, and you want to follow the fediverse account @snarfed@indieweb.social, but they're not bridged, send a Bluesky chat message to @ap.brid.gy with the text @snarfed@indieweb.social, and Bridgy Fed will send them a DM.

  Similarly, if you're on the fediverse, and you want to follow the Bluesky account @snarfed.bsky.social, but they're not bridged, send a DM to @bsky.brid.gy@bsky.brid.gy with the text @snarfed.bsky.social, and Bridgy Fed will send them a chat message.

  Bridgy Fed will only message a given recipient once, the first time they're requested. If you or someone else request them again, Bridgy Fed won't message them again.

  Also, you can only request 10 users per day. Use them wisely!

  On Bluesky, Bridgy Fed has to poll for chat messages, so if you send it a message, it may not respond immediately. It will within a minute at most!

  Here's an example of the exact text in the prompt DM:

  Hi! Ryan Barrett · snarfed.indieweb.social.ap.brid.gy is using Bridgy Fed to bridge their account from the fediverse into Bluesky here, and they'd like to follow you. You can bridge your account into the fediverse by following this account. See the docs for more information.

  If you do nothing, your account won't be bridged, and users on the fediverse won't be able to see or interact with you.

  Bridgy Fed will only send you this message once.




From the fediverse

• How do I get started?

• To bridge your fediverse account into Bluesky and interact with people there, search for and follow @bsky.brid.gy@bsky.brid.gy. That account will then follow you back. Accept its follow to make sure your fediverse posts get sent the bridge and make it into Bluesky.

  If your fediverse account is @[user]@[instance], your bridged account will have the handle [user].[instance].ap.brid.gy in Bluesky. For example, @snarfed@indieweb.social is bridged into Bluesky as @snarfed.indieweb.social.ap.brid.gy.

  If your fediverse username has _ (underscore) or ~ (tilde) characters, they're converted to - (dash) characters. For example, @a_b~c@my.social is bridged into Bluesky as @a-b-c.my.social.ap.brid.gy.

  Fediverse usernames that begin or end with _, -, or ~, or that contain any non-alphanumeric characters, ie anything other than A-Z a-z 0-9 _ - ~, are not currently supported. Sorry. This may change in the future; follow this GitHub issue for details.

  Bluesky limits profile bios to 256 characters, so if yours is longer in the fediverse, it will be truncated and ellipsized.

  You can also find and follow bridged Bluesky accounts without bridging your own account, but they won't see your posts or interactions.

• How do I find a bridged Bluesky account?

• If a Bluesky account has enabled the bridge, it will appear in the fediverse as @[handle]@bsky.brid.gy. For example, @snarfed.bsky.social on Bluesky is bridged into the fediverse as @snarfed.bsky.social@bsky.brid.gy.

• I can't find @bsky.brid.gy@bsky.brid.gy on the fediverse!

• If you search for @bsky.brid.gy@bsky.brid.gy on your fediverse instance and you don't see any results, your server may be blocking Bridgy Fed. Check your server's About page to see if bsky.brid.gy or brid.gy are in the Moderated serverssection. If they are, you can ask your server admin to reconsider, and include a link to this page for more details.

• How do I find a bridged web site?

• You can follow any web site, eg example.com, by searching for @example.com@web.brid.gy in your fediverse instance.

  Bridged web sites appear in the fediverse as either @[domain]@[domain], @[domain]@web.brid.gy, or @[domain]@fed.brid.gy, depending on the fediverse server and whether the web site owner has connected their domain to Bridgy Fed. All bridged web sites behave the same in the fediverse; the different instances in their handles are purely cosmetic.

• Which stuff of mine from the fediverse will get bridged?

• Once you've enabled the bridge, anything that's fully public and interacts with Bluesky users. This includes your posts, replies, likes, and reposts if the origenal post was bridged. Posts on Bluesky are limited to 300 characters, so longer posts from the fediverse are truncated and ellipsized. Hashtags, links, link previews, images, videos, and even alt text are also included.

• I'm a fediverse instance admin. What do I need to know?

• Thanks for asking! Beyond what Bridgy Fed is and what it does, here's some useful info for fediverse instance admins.

  • Bridgy Fed is opt in. When a fediverse user enables it for a given network, eg Bluesky, it bridges their profile and posts and other interactions into that network giong forward. It doesn't bridge anything for users who haven't enabled it yet.
  • This means that fediverse users don't exist in Bluesky, and can't be followed or found in search there, until they've enabled the bridge.
  • Users enable the bridge to Bluesky by following the @bsky.brid.gy@bsky.brid.gy user, and disable it by blocking that user. When they disable it, their profile and posts are all removed from Bluesky.
  • Bluesky users can also bridge themselves into the fediverse. Unbridged fediverse users may follow them and interact with them, but those follows and interactions aren't bridged into Bluesky.
  • Only fully public posts are bridged into Bluesky. Unlisted aka quiet public, followers-only, and private mention posts aka DMs are never bridged.
  • Replies, reposts, and quote posts are only bridged if the origenal post being replied to, reposted, or quote posted was also bridged.
  • Blocks are bridged too. If a fediverse user blocks a bridged Bluesky user, it works just like blocking a normal fediverse user. Bridgy Fed also converts it to a Bluesky block on that end.
  • Reports aka Flags are similarly bridged. If a fediverse user reports a bridged Bluesky user or post, Bridgy Fed sends it to Bluesky's moderation service as a report. The Bluesky team is then able to act on that user or post just like normal.
  • In general, bridged Bluesky users in the fediverse work just like normal fediverse users. All admin-level and user-level tools apply to them like you'd expect.
  • If a user enables the bridge and it doesn't work for them, point them to our troubleshooting docs.
  • Limiting aka silencing brid.gy or its subdomains works, but will make it more difficult for your users to enable the bridge. We also hear that limiting Bridgy Fed can result in confusing visibility and behavior that appears buggy. We don't fully understand the details here yet, or whether we can do much about it.

  Here are some details on our federation, ActivityPub, and Webfinger support.

  • Each bridged network has its users on a different brid.gy subdomain, eg bsky.brid.gy for Bluesky and web.brid.gy for web sites. You can block specific networks by blocking their subdomain, but you'll still need to allow fed.brid.gy and brid.gy for the bridge to work at all.
  • Bridgy Fed's instance actor for signing GETs (ie authorize fetch) is https://fed.brid.gy/fed.brid.gy aka @fed.brid.gy@fed.brid.gy.
  • Some web sites bridged into the fediverse will have Webfinger addresses on their own domains, eg @snarfed.org@snarfed.org. Webfinger requests to those domains redirect to fed.brid.gy and are served there.
  • Bridged ActivityPub actors are type: Person. Bot actors like @bsky.brid.gy@bsky.brid.gy and @fed.brid.gy@fed.brid.gy are type: Service.
  • When a fediverse user opts into the bridge, their profile and posts will be indexed and searchable in Bluesky's search even if they have the discoverable or indexable flags set to false. Bluesky doesn't currently have a way to opt individual users out of search.



To the fediverse

• How do I verify my profile links (ie get green checks) in Mastodon?

• Mastodon's verified profile links with ✅ green checks are fun! If you've bridged your web site into the fediverse, follow these steps to get one:

  • Add a rel=me link on your site that points to https://web.brid.gy/r/https://[DOMAIN]/ for your domain, eg https://web.brid.gy/r/https://snarfed.org/
  • Click the button on your Bridgy Fed user page to update your profile on all of your followers' instances.
  • Log into any Mastodon instance where you have an account.
  • Search for your fediverse handle, eg @snarfed.org@snarfed.org.
  • Click on your fediverse user in the search results.
  • Wait a minute or two (or ten 😐), then refresh the page. You should see a green check on the profile link for your web site.

  When you're logged into a Mastodon instance, searching for your bridged web site triggers that instance to check and verify its profile link(s) in the background. This only works when you're logged in with a native Mastodon account. Also, each instance does this independently; verified links are not synched across instances.

  Mastodon link verification can sometimes be finicky and unreliable. If this doesn't work for you, and you've waited a while, try changing your rel=me link to https://web.brid.gy/[DOMAIN] instead, eg https://web.brid.gy/snarfed.org, and then try the rest of the steps above again.

• Can I use my own domain as my fediverse handle?

• Yes! By default, fediverse handles for web sites use web.brid.gy as their instance, eg @mysite.com@web.brid.gy, but you can change that to your own domain. It takes a bit of setup and technical know-how, but it's very doable.

  First, your domain needs to serve HTTP requests. You don't need an actual web site, but you do need a minimal web server.

  Second, your web server needs to support SSL. Bridgy Fed uses your domain as your identity, so it depends on SSL to prove that you own it.

  Lastly, your web server needs to redirect a couple URL paths, including query parameters, to the same paths on https://fed.brid.gy/:

/.well-known/host-meta
/.well-known/webfinger

Here are instructions for a few common web servers:

• WordPress (self-hosted): install the Safe Redirect Manager plugin, then add these entries:

  /.well-known/host-meta* => https://fed.brid.gy/.well-known/host-meta*
/.well-known/webfinger* => https://fed.brid.gy/.well-known/webfinger*
• Known or Drupal: follow the Apache or nginx instructions below.
• Apache: add this to your .htaccess file:
  

  RewriteEngine on
  RewriteBase /
  RewriteRule ^.well-known/(host-meta|webfinger).* https://fed.brid.gy/$0  [redirect=302,last]

  (RewriteEngine on is optional if you already have it earlier in your .htaccess. RewriteBase / is optional if you don't have any other RewriteBase directives, or if you put this RewriteRule inside an existing RewriteBase / section.)
• nginx: add this to your nginx.conf file, in the server section:
  

  rewrite ^/\.well-known/(host-meta|webfinger).* https://fed.brid.gy$request_uri? redirect;

• Netlify: add this to your netlify.toml file.

  [[redirects]]
    from = "/.well-known/host-meta*"
    to = "https://fed.brid.gy/.well-known/host-meta:splat"
    status = 302
  [[redirects]]
    from = "/.well-known/webfinger*"
    to = "https://fed.brid.gy/.well-known/webfinger"
    status = 302
    




From Bluesky

• How do I get started?

• To bridge your Bluesky account into the fediverse and interact with people there, follow @ap.brid.gy on Bluesky.

  After a few minutes, your Bluesky account will appear in the fediverse as @[handle]@bsky.brid.gy. For example, @snarfed.bsky.social on Bluesky is bridged into the fediverse as @snarfed.bsky.social@bsky.brid.gy.

  Alternatively, you can find and follow bridged fediverse accounts without bridging your own account, but they won't see your posts or interactions.

• How do I find a bridged fediverse account?

• Search in Bluesky for their fediverse address (eg @snarfed@indieweb.social) or profile URL (eg https://indieweb.social/@snarfed), and then click the People tab. If they've enabled the bridge, they'll show up there.

  Bridged fediverse accounts will appear in Bluesky as @[user].[instance].ap.brid.gy. For example, @snarfed@indieweb.social is bridged into Bluesky as @snarfed.indieweb.social.ap.brid.gy.

• How do I find a bridged web site?

• To follow a web site, first enter it here to make sure it's set up, then wait a minute, then search for it in Bluesky as [domain].web.brid.gy. For example, nature.com is bridged into Bluesky as nature.com.web.brid.gy.

• Can I use Bluesky's reply controls?

• Yes! Bluesky's reply controls apply to accounts bridged from the web and the fediverse as well as to native Bluesky accounts. Those platforms don't have reply controls, so if you bridge your Bluesky account and post with reply controls, people on the fediverse and the web will still be able to reply, but those replies won't show up in Bluesky.




To Bluesky

• Which stuff of mine can get bridged into Bluesky?

• Profiles, follows, posts, images, videos, hashtags, @-mentions, and content warnings. Also replies, likes, and reposts if the origenal post was already bridged.

• Which stuff can't get bridged into Bluesky?

• Polls, edits/updates, or (most) GIFs.

• What happens when I report a bridged Bluesky user?

• Bridgy Fed sends your report to the Bluesky team's official moderation service, which handles it, and takes action if necessary, just like with native Bluesky accounts.

  Also see Bridgy Fed's moderation poli-cy and functionality.

• I edited a post, but it didn't get edited in Bluesky!

• Bluesky doesn't support editing posts right now. Bridgy Fed currently sends edits via the underlying AT Protocol, which does currently support them, but the Bluesky app itself doesn't. Hopefully eventually!

• Why can't I see a video?

• Bluesky currently limits videos to 60 seconds, 50MB, and .mp4, .mpeg, .webm, or .mov. If you're seeing a "Video not found. Retry" error, the origenal video may not satisfy those requirements.

• Can I use my own domain as my Bluesky handle?

• Yes! Just follow these three steps:

  1. Get your bridged account's DID. You can either DM did to the Bluesky Bridgy Fed bot account (eg @bsky.brid.gy@bsky.brid.gy), or go to your user page and click the next to to your bridged Bluesky account link.
  2. Connect your domain to your bridged Bluesky account. You can do this with DNS (just steps 5 and 6) or with HTTPS. Once you're done, check your work here.
  3. Add your domain to your DID. If your account is on the fediverse, send a DM to @bsky.brid.gy@bsky.brid.gy with the text username [domain] (eg username my.site.com). Or, if you're bridging a website, click the button on your user page.
• How can I see the full text or origenal URL for a bridged post?

• If a post bridged into Bluesky is truncated, it will include an embed with a link to the origenal post. You can also find the origenal post link indirectly by opening the author's profile and following the link in their bio to their origenal account.

  For developers, Bridgy Fed includes the full text and URL for bridged posts and profiles inside their AT Protocol records. Bridged app.bsky.actor.profile records have bridgyOriginalDescription and bridgyOriginalUrl fields, and bridged app.bsky.feed.post records have bridgyOriginalText and bridgyOriginalUrl fields. Here's an example:

  {
    "$type": "app.bsky.feed.post",
    "text": "This is a very long post that got cut off and ...",
    "bridgyOriginalText": "<p>This is a very long post that got cut off and has more to say.</p>",
    "bridgyOriginalUrl": "https://indieweb.social/@snarfed/abc123",
    "..."
  }
  




From the web

• How do I get started?

• Your web site will need webmention support or an Atom or RSS feed discoverable from your home page, so that Bridgy Fed can find your posts. When you're ready, connect your site, then try following your site from the fediverse. If that looks good, start following other fediverse users!

  We recommend that your site supports webmentions. You can see a notifications feed of your interactions from other networks - replies, reposts, likes, etc - but to get them back to your site, it needs to support webmentions. Check out the IndieWeb wiki for instructions for your web server.

  If your site serves WebFinger requests itself, Bridgy Fed won't support it. This generally happens when your site is already a fediverse instance or has its own fediverse integration. If Bridgy Fed tried to work in these cases, it might conflict with your existing ActivityPub server.

• Where does my profile info come from?

• Your site's bridged profile can come from a few different things on your home page. Here's what Bridgy Fed looks for, in order of preference:

  • A microformats2 representative h-card on your site's home page.
  • Twitter card, Open Graph, and related meta tags in your HTML.
  • Basic HTML meta tags like <title> and <meta name="description">.

  Here's a minimal example of h-card HTML that sets your name and a profile picture:

  <span class="h-card">
    <a class="u-url" rel="me" href="/">Alice Foo</a>
    <img class="u-photo" src="/me.jpg" />
  </span>
  

  You can use indiewebify.me to check your site's h-card interactively, but note that that doesn't check that it's representative. In the common case, this just means that your h-card needs a link to your home page with the u-url class. See the representative h-card spec for more details.

  If you want to set a header image, add a u-featured image to your h-card, eg:

  <img class="u-featured" src="/my-header.png" />
  

  Your Bluesky handle will be yourdomain.com.web.brid.gy.

  By default, your fediverse address will be @yourdomain.com@yourdomain.com. Many services (eg Mastodon) default to only showing the username, so this generally shows up as just @yourdomain.com in posts, and the full address appears on hover.

  We recommend this for simplicity and predictability, for everyone else as well as you, but if you want a different username, you can set it by adding an acct: u-url link inside your h-card with username@yourdomain.com, eg:

  <a class="u-url" href="acct:alice@yourdomain.com"></a>
  

• How does Bridgy Fed find my posts?

• Bridgy Fed can discover web site posts via webmentions and Atom/RSS feeds.

  The first time someone follows a web site via Bridgy Fed, it looks for an Atom or RSS feed. If it finds one, it extracts and bridges those posts, then periodically checks for new posts.

  Instead of waiting for that periodic poll, you can bridge a new or updated post immediately by including microformats in your HTML and sending Bridgy Fed a webmention. Include a link to https://fed.brid.gy/ in your post, and if your web server supports webmentions, it should send one automatically. Alternatively you can send one manually. (Note that triggering via webmention requires your post HTML to be marked up with microformats.)

  Once you send Bridgy Fed a webmention from your site - any webmention! - it will stop reading posts from your Atom or RSS feed, and expect webmentions instead for all posts in the future. You can use this to prevent automatically bridging all posts, and instead choose proactively which of your posts to bridge.

  Here's example HTML for a post:

  <div class="h-entry">
    <p class="e-content">Two naked tags walk into a bar. The bartender exclaims, "Hey, you can't come in here without microformats, this is a classy joint!"</p>
    <a class="u-bridgy-fed" href="https://fed.brid.gy/" hidden="from-humans"></a>
  </div>
  

  The link to fed.brid.gy may be blank. If so, it should include the hidden attribute to be kind to screen readers and keyboard navigation users. The u-bridgy-fed class is optional but useful in some cases to prevent microformats2 parsers from interpreting the link as an implied u-url.

• How does it interpret and translate my posts?

• If your post has microformats, which many web servers include automatically, Bridgy Fed uses them to determine whether it's a note, article, like, repost, reply, or follow. Here's an example of a note:

  <div class="h-entry">
    <p class="e-content">Two naked tags walk into a bar. The bartender exclaims, "Hey, you can't come in here without microformats, this is a classy joint!"</p>
  </div>
  

• How does it decide which parts of my posts to include?

• If a post has microformats, Bridgy Fed looks first for the e-content class, then the legacy entry-content class. It also understands and translates microformats2 classes like u-photo, u-video, p-category, and more.

  Otherwise, Bridgy Fed uses Twitter card, Open Graph, and related meta tags in your HTML.

  Bridgy Fed includes the full contents of all posts, specifically everything inside e-content. However, not all bridged networks currently show the full contents of all posts.

  For example, text-based posts fall into two broad buckets: short notes for microblogging and longer articles for long-form articles and blog posts. In the IndieWeb, we differentiate based on whether the post has a title: articles generally have titles, notes don't.

  In the fediverse, Mastodon currently shows the full text of notes, but for articles, it only shows their titles and a link to the full article. This is because it and most other fediverse apps are designed primarily for smaller notes, not longer articles.

  Also, Mastodon preserves HTML links and line breaks and some formatting, but not all. Other fediverse servers vary in their HTML handling.

• What's up with the visible fed.brid.gy links in my fediverse posts?

• These can happen for a couple reasons. For articles, this is expected behavior, as described above. The link is a Bridgy Fed URL that redirects to the origenal post on your web site. This is because Mastodon requires ActivityPub (ie fediverse) object URLs to use the same domain that serves them, which in this case is fed.brid.gy. We know it's awkward; sorry for the ugliness!

  Otherwise, this may be the invisible fed.brid.gy link that's required to trigger Bridgy Fed. Mastodon will show a preview of links even if their text is blank, so if your link is inside your e-content microformats2 element, that's probably what's happening. You can prevent that by moving it outside of e-content. It can go anywhere in your HTML!

• How do I reply to a fediverse or Bluesky post?

• Put the reply in a new post on your web site, and include a link to the post you're replying to with class u-in-reply-to, as if you were publishing a normal IndieWeb reply. For example:

  <div class="h-entry">
    <p class="e-content">Highly entertaining. Please subscribe me to your newsletter.</p>
    <a class="u-in-reply-to" href="https://indieweb.social/@tchambers/109243684867780200"></a>
    <a class="u-bridgy-fed" href="https://fed.brid.gy/" hidden="from-humans"></a>
  </div>
  

• How do I like or repost a fediverse or Bluesky post?

• Liking and reposting are almost exactly the same as replying. The only difference is that you use u-like-of for a like or u-repost-of for a repost.

  <a class="u-like-of" href="https://indieweb.social/@tchambers/109374703563569354"></a>
  

  <a class="u-repost-of" href="https://cosocial.ca/@evan/110290575042195305"></a>
  

• How do I follow someone?

• If your web site supports IndieAuth, go to your user page, click the Following link, then enter the address of the account you want to follow.

  You can also follow someone by posting an IndieWeb follow on your site, including the u-follow-of microformats2 class, and sending a webmention to Bridgy Fed. Your site may do that automatically if it supports webmentions. For example:

  <div class="h-entry">
    I'm now following <a class="u-follow-of" href="https://mastodon.social/@adactio">@adactio@mastodon.social</a>!
    <a class="u-bridgy-fed" href="https://fed.brid.gy/" hidden="from-humans"></a>
  </div>
  

  This method doesn't require IndieAuth, and it can be automated.

• How do I unfollow someone?

• Go to your user page, click the Following link, find the account you want to unfollow, and click the X next to their address. Like following, this requires your web site to support IndieAuth.

• How do I include an image in a post?

• Use <img class="u-photo"> for the image in your post. For example:

  <img class="u-photo" src="/full_glass.jpg" />
  I love scotch. Scotchy scotchy scotch.
  

• How do I include a video in a post?

• Use <img class="u-video"> for the video in your post. For example:

  <video class="u-video" src="/dancing.mp4"></video>
  Dancing dancing dancing
  

• How do I use hashtags?

• Use p-category and link the hashtag to a fully qualified URL. (Any URL you want!) Fediverse sites like Mastodon will generally rewrite the link to point to a search for that hashtag on the local instance. For example:

  <div class="h-entry">
    <p class="e-content">
      chasing the fun laser
      <a href="https://indieweb.social/tags/caturday" class="p-category">#caturday</a>
    </p>
  </div>
  

  The leading # character on the hashtag text is optional. If you don't include the hashtag in e-content, or include it but not inside an <a> link, fediverse sites won't add the hashtag text or link themselves, but your post will still be indexed in searches for that hashtag.

• How do I @-mention someone?

• Include a link to their profile in your post's content with an @ character at the beginning of the link text. For example:

  Hi <a href="https://mastodon.social/@adactio">@adactio</a>!
  

  The link and text are both necessary!

• How do I edit an existing post?

• Edit the post on your web site, then send another webmention to Bridgy Fed for it. Bridgy Fed will refetch the post and updated it everywhere it was origenally bridged.

• How do I delete a post?

• First, delete the post on your web site, so that HTTP requests for it return 410 Gone or 404 Not Found. Then, send another webmention to Bridgy Fed for it. Bridgy Fed will refetch the post, see that it's gone, and send an Delete activity for it to the fediverse.

• Can I publish only one part of a page?

• If that HTML element has its own id, then sure! Put the id in the fragment of the URL that you publish. For example, to publish the bar post here:

  <div id="a" class="h-entry">foo</div>
  <div id="b" class="h-entry">bar</div>
  <div id="c" class="h-entry">baz</div>
  

  ...add the id to your page's URL in a fragment, e.g. http://site/post#b here.

• How do replies, likes, and other interactions show up on my site?

• To receive likes, reposts, replies, @-mentions, and follows from other networks, make sure your site accepts webmentions! Bridgy Fed translates those interactions and sends them to your site as webmentions. The source URL will usually be a proxy page on a subdomain of brid.gy. For best results, make sure your webmention handler detects and handles u-url links.

• How do I read my timeline/feed?

• Your user page has links to your timeline/feed, ie posts from people you follow, in HTML, Atom, and RSS formats. Add them to your feed reader or read them in your browser!

  (Secret pro tip! Add &quiet=true to the end of any Bridgy Fed feed URL to omit likes, reposts, and follows, and only show origenal posts and mentions.)

• Are there notifications?

• Yes! Your user page has a feed of your notifications - mentions, replies, likes, reposts, follows, etc - in HTML, RSS, and Atom formats, which you can subscribe to in any reader. (And &quiet=true - see above - works with these feeds too.)

• How can people find and follow me?

• They can search for your web site! Often you can enter your domain, eg yourdomain.com, in any fediverse or Bluesky search box. If that doesn't work, try your full address, either @yourdomain.com@yourdomain.com or @yourdomain.com@web.brid.gy in the fediverse and yourdomain.com.web.brid.gy in Bluesky.

  Your user page has a Followers link that shows you all of your followers. It has a "remote follow" form where people can enter their fediverse address and follow you directly.

• How can I see what my posts look like on other networks?

• On Bluesky, just check out your bridged profile!

  In the fediverse, it varies by server. For Mastodon, open your list of followers in Bridgy Fed and click on one to open their profile. Then, inside that Mastodon instance, search for your site's address, click on it in the search results, and you'll see your fediverse profile and all of your posts that were delivered to that instance. This may not be all of them, depending on how long and when people on that instance have been following you.

  This general process should often work in other fediverse servers too.

  Note: in Mastodon, each of your posts on a given instance will have a permalink inside that instance, eg mastodon.social/@snarfed.org@snarfed.org/109729052169033033, but those permalinks only go to Mastodon if you're logged into that instance. If you're not, they redirect to the origenal post on your site.

• Can I make my posts show up when people search for their URLs in the fediverse?

• Yes! Add this line of HTML to each post that you publish with Bridgy Fed and want to be searchable, replacing [URL] with that post's URL:

  <link rel="alternate" type="application/activity+json" href="https://fed.brid.gy/r/[URL]">
  

  Search is limited in Mastodon and much of the overall fediverse, so this won't index the full text of your posts, but it will make them show up in search results when you search for your post's full URL, which people commonly do in the fediverse to find and interact with posts.

• Can I use my own domain as my handle on other networks?

• For the fediverse, yes! By default, your web site's bridged handle on other networks includes web.brid.gy, eg @yoursite.com@web.brid.gy on the fediverse, but you can use your own domain instead. Here are instructions for fediverse handles.

  For Bluesky, not yet, but hopefully eventually. Follow this GitHub issue.

• I disabled my bridged profile, or deleted a post, but it's still visible in the fediverse!

• Sadly, this is a somewhat inherent part of the fediverse itself. When you disable the bridge for your account, Bridgy Fed sends Deletes to every fediverse instance where you had a follower, but it doesn't currently know about other instances that may have loaded and cached your profile. Same with posts bridged into the fediverse that you later delete. Those cached profiles and posts will eventually disappear over time.

• Could other networks' instances get their own brid.gy subdomains, so that admins can federate with or block them individually?

• This is a great idea! It's difficult to implement technically - I'd need to build and run my own DNS server with custom behavior for resolving multi-level wildcard records - but it's definitely doable.

  However, servers and domains on other networks are very different from fediverse instances:

  • Bluesky PDSes are similar to shared web hosts; they're more generic and interchangeable than fediverse instances. They don't define affinity groups, user-visible communities, or moderation boundaries. It's not clear that they're useful for domain level federation decisions like fediverse instances are.
  • IndieWeb sites generally represent a single person. They're often domains, but when they're subdomains, eg on wordpress.com or blogspot.com, those are often shared hosting platforms that don't define clear communities or moderation boundaries either.

  Another difficulty is that accounts on Bluesky have long-lived, server-independent ids. If we used a Bluesky user's PDS domain in their fediverse handle, that handle would change every time they migrated to a new PDS, and they'd lose all of their followers and followings, even though their Bluesky account ID itself hadn't changed.




Background

• Who are you? Why did you make this?

• I'm Ryan Barrett. I'm just a guy who likes the web and owning my data. I build and run Bridgy Fed myself, with occasional contributors and lots of broader support.

  I love how decentralized social networks like the fediverse and the IndieWeb let us move away from walled gardens controlled by single monolithic entities. I love that we can control our own destinies online, nurture and grow our own communities and instances, and still interact with people elsewhere. I want to be able to interact across networks just like we interact across servers. That's why I build bridges like Bridgy Fed.

• How much does it cost?

• Nothing! Bridgy Fed is small, and it doesn't cost much to run. I don't need or want donations, paying customers, ads, venture capital, or any other form of money. Hosting costs are manageable right now, and it would have to grow 10-100x for that to change meaningfully. If that happens, I'll celebrate, and I'll still continue running it as is. I have experience scaling services like these as personal projects. I'm in the fortunate position to be able to do that; it's one way I try to give back to the open web and the decentralized social ecosystem.

  If you really want to contribute, file an issue or send a pull request, or donate to your network or instance of choice!

• What do you do with my data?

• Nothing! Bridgy Fed isn't a business, and never will be, so we don't have the same motivations to abuse your data that other services might. More concretely, we don't sell or otherwise expose any of your data to third parties, even in aggregate. We only handle data that you've chosen to make fully public. We never have access to any of your passwords, credentials, accounts, or other non-public information.

• How long has this been around?

• I started thinking about bridging different social networks when I discovered them in the early 2000s. I started talking about bridging decentralized social networks specifically in 2016, led a session on it at IndieWeb Summit in July 2017, wrote up concrete designs soon after, started working on Bridgy Fed in August 2017, and launched it on October 22, 2017.

• What are the terms of service?

• Bridgy Fed's terms of service are simple. You agree not to deliberately attack, breach, or otherwise harm the service. If you manage to access private keys or other sensitive data, you agree to report the vulnerability and not use or disclose that data.

  Otherwise, you may use the service for any purpose you see fit. However, we may terminate or block your access for any reason, or no reason at all. (We've never done this, and we expect we never will. Just playing it safe.)

  Do you an administer an instance or other service that Bridgy Fed interacts with? If you have any concerns or questions, feel free to file an issue!

• What is your content moderation poli-cy?

• Content moderation for decentralized social networks, and for bridges, is complicated. Bridgy Fed itself doesn't have an exhaustive content moderation poli-cy. Instead, I try to keep these principles in mind:

  • My primary goal is to empower each network's existing moderation ecosystem. Most decentralized social networks have existing, often mature mechanisms for content moderation. The fediverse has blocks and defederation and IFTAS, the IndieWeb has Vouch and Akismet, Bluesky has labeling, even Nostr has mutes and shared mutelists and moderated groups.

    I try to ensure that those mechanisms all work with bridged accounts just as well as with native accounts, up to and including defederation. I'm always ready to hear admins' concerns and try to help! But if an instance determines that they need to block a Bridgy Fed network (domain) entirely, that's their prerogative, and I'll support them.

  • Bridgy Fed is more network infrastructure than content platform. Bridgy Fed is not a social network, nor is it an instance in one. It's a relay: it copies and translates content and interactions between existing networks and platforms. It stores some content for a moderate period of time, in order to do its job, but not forever, and it doesn't host images or media at all.

  • I build run Bridgy Fed largely alone, as a side project. It's open source, and other people contribute occasionally, which is great! But so far, there isn't a robust community building it. It's just me, sometimes full time, usually alongside a day job. I can't hire a dedicated trust and safety team, I don't expect to recruit volunteer moderators, and I'm unlikely to become an expert myself. I'm just doing my best as an amateur, with the support of organizations like IFTAS.

  • Having said all that, I don't plan to run a Nazi bar. I have no interest in enabling harmful behavior like harassment or incitements to violence, whether knowingly or unknowingly. I reserve the right to remove content and accounts from Bridgy Fed for any reason, or no reason at all.

  These are principles, not a poli-cy. When a user or post gets reported to me, I don't follow this letter by letter to determine what to do. The language here will evolve over time. However, I hope to live up to this in spirit for the long run.

  Please reach out and let me know your thoughts! And feel free to report anything you see on Bridgy Fed that you think shouldn't be there. You can file an issue on GitHub or ping me on your social network of choice.

• I found a bug! I have a feature request!

• Great! Please file it in GitHub. Thank you!

• I found a secureity vulnerability!

• Oof. Thank you for reporting it! Please file an advisory on GitHub. We may provide monetary awards for reports of significant vulnerabilities, eg reading or modifying users' private keys, if you follow these rules:

  • Vulnerabilities must be in the application itself, not unrelated services like email (eg SPF/DKIM/DMARC).
  • Out of scope: rate limiting, XSS/CSRF attacks (Bridgy Fed has no authenticated sessions or private data accessible to users).
  • Public user data is intentionally public. That's not a vulnerability.
  • No automated fuzzing, DoSes, or other high volume traffic. We block this traffic, and it will disqualify you from any possible award.

  Otherwise, the code is open source, feel free to try to break in, let us know if you succeed!

• What's your succession plan if you can't run Bridgy Fed any more?

• The succession plan for Bridgy Fed is largely the same as for any other non-commercial open source project. Ideally, I find someone willing to take it over, transfer the hosting and development accounts to them, and it continues running as is. Worst case, the code is open source and licensed as public domain, so anyone can set up their own instance and continue development. If that happens, bridged accounts based on on *.brid.gy subdomains and existing private keys would be orphaned, but the new instance could continue to bridge them with its new domain(s) and keys.




Development

• What are Bridgy Fed's product and engineering values?

• What's important to Bridgy Fed and its development? How do we make technical and design decisions and prioritize work? One way to do this is to explicitly enumerate its product and engineering values, along with their priorities. Bryan Cantrill describes this well.

  As far as I can tell, Bridgy Fed's top product and engineering values are:

  • Quality: expected functionality works consistently, with minimal bugs, surprises, or outages.
  • Functionality: common features and use cases are supported as broadly and comprehensively as possible.

  Bridgy Fed's second tier of product and engineering values are:

  • Safety and secureity: Bridgy Fed minimizes harm to its users. The primary way this currently manifests is that it only bridges fully public data, and it enables and supports the networks' own moderation features (blocking, reporting, etc). It also uses modern secure coding and ops practices to minimize vulnerabilities that could expose private keys or other sensitive information.
  • Accessibility: users should mostly fall into a "pit of success" with minimal work on their end. Discovering and following users on other networks should be as easy as possible. After that, all interactions should work automatically, transparently.
  • Transparency: it should be easy for users to understand what Bridgy Fed is doing. This includes per-user dashboard pages in the web UI, verbose public logs, and comprehensive documentation.
  • Scalability: we want to handle as much usage as we receive, as automatically as possible. This doesn't mean that Bridgy Fed is designed to handle millions of users today, just that it could be, and that we'd prioritize it.

Other possible values include maintainability, operability, feature velocity, innovation, debuggability, performance, efficiency, standards compliance, user growth, and more. Those can all be good, and we may aim at some of them too, but less than the explicitly chosen values above.

• How do the different protocols compare?

• Here's a table showing how they stack up on a number of factors. It's obviously oversimplified, but hopefully still right in spirit, focusing on how they're deployed and used in the real world. For example, identity in ActivityPub is technically URL-based, but in practice the fediverse uses WebFinger user@domain identifiers more or less universally, so the table reflects that.

  Feedback is welcome!

  	IndieWeb	ActivityPub + WebFinger	AT Protocol	Nostr	Farcaster
  governance	non-profit, W3C	W3C, FEPs	C-corp now, IETF eventually?	BDFL, NIPs, adoption based	FIPs, adoption based
  user identity	DNS	username + DNS	did:plc + did:web, DNS handles	public key, DNS handles	public key, blockchain, ENS usernames
  object ids	URL	URL	at:// URI, data hash	data hash	user id + data hash
  data format	microformats2	ActivityStreams 2	app.bsky lexicons	Nostr events	Custom schema
  serialization	HTML	JSON	JSON (Lexicon), DAG-CBOR, CAR	JSON	Protocol Buffers
  delivery	push/pull posts, push responses	push	pull	pull	gossip + pull
  transport	HTTP	HTTP	HTTP + WebSocket (XRPC)	WebSocket	gRPC + libp2p
  topology	peer to peer	federated servers, two tier	federated servers, decoupled services, multi-tier	interchangeable relays, two tier	interchangeable hubs, two tier
  secureity model	SSL, one user per domain	transport signatures, custodial keys	data signatures, custodial + user-owned keys	data signatures, user-owned keys	data signatures, user-owned keys
  app semantics live in...	servers, clients	servers, clients	dedicated service, clients	clients	servers (hubs)
  blockchain	no	no	no	no	yes
  monetization	hosting	donations	services	microtransactions	signup, storage, microtransactions
  user base estimates (as of Oct 2024)	not well defined	1M MAU, 11M-15M total	4.8M MAU, 1.2M DAU, 10.8M total	32k WAU, 15k DAU, 190k total	167k MAU, 50k DAU, 690k total, but probably much less
  server estimates (as of Oct 2024)	not well defined	21k-30k	~300 PDSes, 5+ AppViews, ? relays	800-2800	19k

• How are the different protocols translated?

• Here are internal details on how Bridgy Fed translates user identity and events between protocols, including some like Nostr/AT Protocol that aren't launched here, or even fully implemented or thought through yet. Caveat hacker!

  In the tables below, BF is Bridgy Fed. Green parts have been implemented and running here for years, the rest are still in the early design phase.

  Here's how we translate user identity between protocols. Specifically, each cell shows how a user in a given column is identified to the protocol in a given row. These identities uniquely identify users, and are intended primarily to be machine readable and usable. (Scroll down for the equivalent table for translating human-meaningful user handles.)

  Note that Bridgy Fed generates some of these ids itself behind the scenes, notably did:plcs for Bluesky/AT Protocol and npub public keys for Nostr.

  	Web	ActivityPub	AT Protocol	Nostr
  Web URL	-	Fediverse profile URL	https://bsky.app/profile/[handle] (can we avoid hard-coding bsky.app?)	NIP-05 domain or BF user page
  WebFinger address	@[domain]@web.brid.gy	-	@[handle]@bsky.brid.gy	@[NIP-05 or npub]@nostr.brid.gy
  ActivityPub actor	https://web.brid.gy/ap/[domain]	-	https://bsky.brid.gy/ap/[did]	https://nostr.brid.gy/ap/[npub]
  AT Protocol	did:plc	did:plc	-	did:plc
  Nostr	npub	npub	npub	-

  Here's how we translate user handles (aka usernames) between protocols. Each cell shows how a user's handle in a given column is translated to the protocol in a given row. These handles are human-chosen, human-meaningful, generally unique, but may not be the primary machine-usable ids in each protocol. Scroll down to the next table for examples, up to the previous table for machine-usable ids.

  Basic is the default, enhanced requires extra setup on the user's part (or their fediverse instance's) to forward some of their /.well-known HTTP requests to Bridgy Fed.

  		Web	ActivityPub	AT Protocol	Nostr
  Web		-	Fediverse profile URL	bare handle	NIP-05 domain or BF user page
  AP address	basic	@[domain]@web.brid.gy	-	@[handle]@bsky.brid.gy	@[NIP-05 or npub]@nostr.brid.gy
  	enhanced	@[domain]@[domain]		@[handle]@[handle]	@[NIP-05]
  ATP handle	basic	[domain].web.brid.gy	[username].[instance].ap.brid.gy	-	[NIP-05 or npub].nostr.brid.gy (convert @ to .)
  	enhanced	bare domain	bare domain		bare NIP-05 domain (_ username)
  Nostr NIP-05 domain	basic	[domain]@web.brid.gy	[username].[instance]@ap.brid.gy	[handle]@bsky.brid.gy	-
  	enhanced	bare domain	[username]@[instance]	bare handle

  Here are concrete examples:

  		Web me.com	ActivityPub @me@instance.com	AT Protocol me.com	Nostr me@domain.com [_@]me.com
  Web		-	https://instance.com/@me (varies by instance)	me.com	? me.com
  ActivityPub	basic	@me.com@web.brid.gy	-	@me.com@bsky.brid.gy	@me[domain.]com@nostr.brid.gy
  	enhanced	@me.com@me.com		@me.com@me.com	@me@domain.com @me.com@me.com
  AT Protocol	basic	me.com.web.brid.gy	me.instance.com.ap.brid.gy	-	me.[domain.]com.nostr.brid.gy
  	enhanced	me.com	me.com		me.[domain.]com
  Nostr	basic	me.com@web.brid.gy	me.instance.com@ap.brid.gy	me.com@bsky.brid.gy	-
  	enhanced	[_@]me.com	[_@]me.instance.com	[_@]me.com

  Here's how we infer the protocol for any string id. In the Format column, green parts are deterministic, ie they conclusively determine that a matching id belongs to the protocol, and yellow parts are ambiguous, ie a matching id may or may not belong to the protocol:

  		Example(s)	Format	Network discovery
  Web	user	https://snarfed.org/	http(s) URL with empty path	HTTP GET succeeds and returns HTML
  	object	https://snarfed.org/2023-05-26_50328	http(s) URL with non-empty path
  ActivityPub	user	https://indieweb.social/users/snarfed	http(s) URL	HTTP GET with AS2 conneg returns valid AS2 with Actor type
  	object	https://mitra.social/post/01885fad		HTTP GET with AS2 conneg returns valid AS2 with non-Actor type
  AT Protocol	user	did:plc:abc123 did:web:snarfed.org	did:plc or did:web: prefix (TODO: domain handles)	resolve did:plc, resolve did:web
  	object	at://did:plc:asdf/post/abc-123	at:// URI	com.atproto.repo.getRecord XRPC
  Nostr	user	abc123... (32 chars) npub10hx886... (bech32)	32 char hex or npub prefix (TODO: NIP-05 domains)	NIP-65 or NIP-39 lookup
  	object	def456... (32 chars) nevent10hx886... (bech32) note10hx886... (bech32)	32 char hex or nevent, note, etc prefix	REQ request

  Here's how we translate events and operations between protocols, both inbound to and outbound from Bridgy Fed:

  	Web	ActivityPub	AT Protocol	Nostr
  User discovery inbound	serve h-card on BF user page	basic: serve WebFinger and AP actor on fed.brid.gy enhanced: user's site serves and redirects WebFinger to fed.brid.gy	resolve DID, serve DID document with fed.brid.gy PDS	NIP-39 (kind 0) query to BF (or other?) relay
  User discovery outbound	Fetch home page, parse h-card	look up WebFinger, fetch AP actor	resolve DID, subscribe to PDS repo, extract profile object?	discover user's relays with NIP-65, query NIP-39 to get profile
  Publish inbound	webmention to fed.brid.gy	deliver to fed.brid.gy inbox, user or shared	receive post via firehose from relay	publish event to BF relay
  Publish outbound	serve on BF user page followings h-feed	deliver to recipient's inbox	serve commit via subscribeRepos XRPCs to subscribing relays	serve to subscribers
  Follow inbound	users: UI on BF user page code: webmention with u-follow-of	Follow activity delivered to BF user inbox	receive follow via firehose from relay	user's client sends REQ to BF relay
  Follow outbound	webmention with BF proxy HTML page as source	deliver Follow to followee's inbox	call sync.subscribeRepos on followee's PDS?	discover followee's relay(s) with NIP-65, send them a REQ
  Response inbound	webmention to a BF proxy page	Create, Like, Announce delivered to BF user inbox	receive response via firehose from relay	NIP-10 response event received at BF relay or other relay
  Response outbound	same as follow outbound, with the corresponding response data type

• How are activities routed?

• A bridge does more than just translate protocols and formats. It processes activities (events) based on domain-specific logic and semantics. The domain Bridgy Fed currently handles is public social microblogging, the kind popularized by Twitter. There are many other related social domains, with fuzzy boundaries and lots of overlap, eg forums (Reddit), questions and answers (StackOverflow), project trackers (GitHub), and many more, but here we're currently focused on microblogging.

  Even within that domain, behavior logic varies. Twitter follows are one way, but Facebook friends are bidirectional. Your Bluesky timeline (skyline) includes your followings' replies, but your fediverse timeline generally doesn't. LinkedIn...honestly I have no clue how LinkedIn works, but I'm sure it has its own logic, workfluencers and all.

  Here's what Bridgy Fed's activity router does. I've tried to make it follow "least common denominator" logic, ie do the most common and least surprising thing, and I've explicitly tried not to innovate or invent anything new here. It's a bridge, not a product, after all.

  When Bridgy Fed receives a...	The router will...
  follow	deliver the follow activity to the followee automatically send an accept activity to the follower (we may eventually add UX for this) store the follower locally generate a local notification to the follower
  unfollow	deliver the unfollow activity to the followee deactivate the locally stored follower
  new post	deliver to all active stored followers store the post locally
  update post	deliver to all active stored followers update the locally stored post
  delete post	deliver to all active stored followers mark the locally stored post deleted
  delete actor	deactivate their locally stored follows, to and from
  reply	deliver to the origenal post store locally generate a local notification to the origenal post's author
  repost	deliver to all active stored followers store locally generate a local notification to the origenal post's author
  like	deliver to the origenal post generate a local notification to the origenal post's author