# Slack Bridges: What are they?
:link: **Shortlink:** [`link.civictech.ca/about-bridges`](http://link.civictech.ca/about-bridges)
The purpose of this document is to help members of Slack communities understand how their special **bridged channels** work.
If you've found yourself on this page, please do feel free to contribute improvements!
Note: This page is used for **many different bridges** so for info specific to your channels, best to keep it elsewhere :tada:
Q: **What is a "bridged channel"?**
A: A bridged channel (or "bridge") is a special channel in which messages/edits/deletions are relayed to and from other special channels on each participating Slack team. The bridge can be simple (connecting 2 teams) or complex (connecting every brigade Slack). Bridges help us communicate between groups from the comfort of our own digital homes (ie. our Slack teams).
Q: **How is this different from a normal channel?**
A: Due to how the bridge works, there are a few caveats you might want to know about:
- **Reaction emoji can't go through the bridge.**
- **Recommendation:** "react" using typed emoji in messages.
- **Threaded replies become "unthreaded".** Basically, they show up as normal messages to everyone else. This means that folks on the other side of the bridge might not have as much context as you see. This is particularly important to remember when replying in very old threads.
- avoid threaded conversations, and
- add context clues to replies, like formatted quotes (by starting lines with `>`) or "re: some context."
- **Notifications can get noisy.**
- `/mute` or leave the channel on one side of the bridge.
- **Auto-completion of @mentions can be awkward.** The users on the other side of a bridge are not actually members on your slack -- the bridgebot impersonates them. If the user exists across a bridge, Slack will notify them and hyperlink their @username as usual.
- start remembering @usernames :smiley:
- with admin access, you could add a "dummy" bot user for commonly-addressed people across a bridge, allowing auto-complete. <sup>(#Footnotes)</sup>
- [possible future mitigation](https://github.com/42wim/matterbridge/issues/361)
- **Messages shared into the channel can't have accompanying text.** If you add additional text with the share, only the additional text is sent through.
- Add your comments in new message after a simple share.
- Help fix [this bug](https://github.com/42wim/matterbridge/issues/369#issuecomment-364272229).
Q: **Who maintains this bridge?**
A: This bridge is an independent effort on behalf of [Patrick Connolly](https://twitter.com/patconnolly), a co-organizer with Civic Tech Toronto. Having said that, he would love for others to be involved, and for this to become a cross-cutting project! (Please do reach out!)
Q: **Why not use Slack's built-in "Shared Channel" feature?**
A: The are a couple limitations of Shared Channels:
- At the moment, they only allow connecting between two teams.
- Only paid teams can create them.
- They will likely never allow connecting non-Slack chat tools. (Our software does: IRC, Riot, Rocketchat, Telegram, etc.)
Q: **How does this bridge work?**
A: Bridges tend to be a tool separate from Slack. There are a few different tools available, but we use **Matterbridge**, which we self-host on Heroku. The best technical documentation of our setup is in the git repo for our Heroku app, [`matterbridge-heroku`](http://github.com/edgi-govdata-archiving/matterbridge-heroku#readme).
Q: **I have another question. Where do I ask it?**
A: Feel free to add it to this doc, or message @patcon on your Slack or [on Twitter](https://twitter.com/patconnolly) :smiley:
<sub>1. This dummy bot will squat their username, which could be confusing if they later try to join your Slack.</sub>