Slacking from Irssi


My IRC client helps me work efficiently and minimize distraction. Over the years, I’ve configured it to behave exactly how I want: Notifying me when topics I care about are under discussion, and equally as important, refraining from notifications that I don’t want. Since my IRC client is developed under the GPL, I have confidence that the effort I put into customizing it to improve my workflow will never be thrown out by a proprietary tool’s business decisions.

But the point of chat is to talk to other humans, and a lot of humans these days are choosing to collaborate on Slack. Slack has its pros and cons, but some of the drawbacks can be worked around using open technologies.

Do you need to Slack from irssi?

If you feel ambivalent toward the web UI, going to the trouble of setting up an IRC client for Slack will likely be more hassle than reward.

If you loathe the Slack UI but don’t care much for IRC, you might be better off considering the Matrix bridge or seeking out other clients. I have not tried them and can’t vouch for any.

If you use WeeChat, you can use Slack IRC directly, or try the WeeChat Slack gateway. A friend at a larger company informs me that the latter doesn’t hold up well on Slack workspaces in the tens of thousands of users, so if you’re on a particularly large Slack you might be better off treating it as an IRC server.

If you’re looking for a terminal-based client to get started with IRC, consider choosing WeeChat over Irssi. WeeChat is extensible in more languages and allegedly has fewer edge cases like the saga detailed here.

The IRC bridge won’t work on all Slacks

First, a word of warning: You can only Slack from IRC if a workspace owner enables the IRC/XMPP gateway for a given instance, which is disabled by default because Slack distrusts users’ ability to make good security decisions. They’re not necessarily wrong, but generally users who care deeply enough to slog through their misleading instructions also know a thing or two about SSL.

This will work on all IRC clients, But...

The good news is that once a Slack instance is exposing the IRC gateway, it looks to an IRC client just like a single standalone IRC server.

The bad news is that the instructions Slack provides will only work if you do them on an IRC client where you weren’t connected to any other IRC yet. This is because (at time of writing) they tell you only to add Slack as a server in your client.

Irssi is “special”.

Let’s step back to the basics of how IRC works for a minute: On IRC, a network is a group of servers, and on a given network you can join various channels. Being on a network is intentionally agnostic of what server you’re connected to, so that if one server goes away, you can connect to another and keep right on chatting.

All modern IRC clients that I’m aware of allow you to be connected to several networks at once. For instance I’m on the Freenode IRC network to talk to people about FOSS projects I use, and also the Mozilla IRC network because most of my work channels are there. Every command you issue to irssi is done in the context of some network – do you want to auth to services? Join a new channel? Add a server? Irssi assumes that the server of the buffer in which you issue a command is the server you want the command to apply to, though some might require you to explicitly specify the network.

So, if you’re already on a network and you tell your client to add a server, what will happen? That’s right, your client will do the smart thing and add the server to the network. It will also likely connect you to that server, and do all the things on that server which you’ve asked it to do when you first connect to that particular network.

What happens if that new server is not part of the network in question at all, but is instead Slack? irssi will do the automatic things, like joining channels and trying to auth to services, that it’s supposed to do when it joins that network anyways, because you as a human told the client that the server was on the network. Even if that’s because some mean ol’ documentation tricked you into it, irssi doesn’t know any better.

What happens when irssi autojoins a bunch of channels, but issues those join commands to the Slack server? Well, on Slack just as on IRC, the first person to join a channel creates it. So, you have just revealed to your whole Slack workspace exactly the names of the channels you were in on the IRC server from which you issued the /server command.

Spuriously creating a bunch of channels isn’t the end of the world, you can just delete them, right? Well, if you have owner or admin permissions on the Slack workspace, absolutely! If you are not an owner or admin, you will have to go find someone who is and ask them to clean up the mess.

Well, at least that’s what happens when an active IRC user blindly assumes that whoever wrote the Slack IRC connection instructions had tried them in an irssi instance they were actually using for IRC. My bad.

Don’t follow the Slack docs verbatim from Irssi.

When you’re looking at, it has instructions like the following:

  1. Ensure that your IRC client is configured with your normal Slack username as your nick.
  2. If you are connecting through a raw /server command, your command will be: /server 6667 myserver.Nosh5Neevot5Efua
  3. If you have a more UI-oriented setup, your IRC server is, and the server password is myserver.Nosh5Neevot5Efua. Accepted ports are 6667, 6697, and 8000.

That Nosh5Neevot5Efua bit is a password you shouldn’t share with anyone – for this post I’m using a string from pwgen so it looks more like the actual config.

To avoid the tale of woe that I outlined above, if you’re slacking from Irssi, you need to add a network before adding the server. This changes the steps to:

  1. Ensure that your IRC client is configured with your normal Slack username as your nick.
  2. Add a network with the command /network add myslack
  3. If you are connecting through a raw /server command, your command will be: /server add -auto -network myslack 6667 myserver.Nosh5Neevot5Efua

See the irssi docs for more options. Join the desired channels on the Slack network just as you would in IRC. When you’re done, remember to /save, and your .irssi/config should contain something like:

servers = (
    address = "";
    chatnet = "myslack";
    port = "6697";
    use_ssl = "yes";
    ssl_verify = "no";
    autoconnect = "yes";
    password = "mozilla.Nosh5Neevot5Efua";

chatnets = {
  myslack = { type = "IRC"; };

channels = (
  { name = "#slackchannel"; chatnet = "myslack"; autojoin = "yes"; },

Now Slack is almost IRC

With the bridge set up, Slack behaves mostly like IRC. There remain some outstanding differences:

  • You cannot leave the workspace’s default channel. You can mute the channel or turn off notifications but Slack won’t let you leave.
  • When someone uses @here in a channel, Slack appends your username to the end of the message when forwarding it along to IRC to make sure you get pinged. The person did not actually type your nick when it occurrs in this context.
  • If you want to hilight a Slack user in a message, you must inlcude the @ in their username. If you just say the string of their name, they won’t get notified. This is the opposite of IRC, where it’s a newbie mistake to include someone’s hat when addressing them.
  • Slack has message threading and allows editing and deleting messages, neither of which are really a thing on IRC. Remember that Slack sends the first version of each message to the IRC bridge. Messages in a thread will look like they were sent to the channel. Messages that were later deleted will persist in your IRC logs. Edits won’t show up; IRC bridge users see only the first version of each. If you need to view an edited message or edit or delete your message, you have to use the Slack UI.

Have fun!