Personally, I like Zulip way better than Slack because of how it does message threads: _channels_ that have conversations in _topics_ "makes sense" to me.

Pros: Server maintenance is blissfully minimal. Message threading that actually works. No server issues or downtime in the past 4 years. (Every time I see a HN "Slack is down" posting, I smile to myself and continue my work day...) It runs great for ~50 employees on an AWS t3a.large instance. Importing all the company's previous messages from Slack worked perfectly.

Cons: If you have people used to Slack, there will be resistance / a learning curve. Knowing, "when do I create a topic?" takes practice. The mobile and desktop apps are not as polished as Slack's. Not as many integrations as Slack. You have to know enough to manage and secure a server yourself.

The Zulip devs accept Github donations, btw, if anyone cares to support their work. (We do; no affiliation other than we're happy to have a private, self-hosted alternative.)

edits: punctuation and adding that instance was a ".large"

We use it at work. We first switched over to Mattermost, then to Zulip. Mattermost seemed like a clone of Slack and we were initially "satisfied", but didn't see it get improved that much nor noticed any attempts of it trying to tackle other problems. Then they raised their prices to even higher than Slack's, which we took as a bit of dick move seeing as we were self-hosting it + it has nowhere near the experience of Slack. Push notifications in general didn't seem to be that good.

Zulip has a nice spin on the way discussions work with their concept of "topics". It lends itself well to how we conceptualize the discussions across our development teams, without unnecessarily creating many ad-hoc temp channels (something we'd have done on Slack). We're liking it thus far. That being said I do need to check why it's using about 35 gigs of RAM on our server.

Clojurians-Zulip is much better interface to catch up and read through existing information than Clojurians-Slack ever was (Clojurians is basically bunch of Clojure(Script) people helping/getting help from each other), for whats it worth. Best would be if they both could be fully public, but for now the archives seems to do the job well at least.

Sort of a weird context to ask for Zulip recommendations, but sure. I find Slack to be a miserably unproductive experience that makes it impossible to keep up with a team (or teams) of any significant size. Slack is good for recreation, not productivity. If the primary purpose of your organization is to be a social group, then by all means use Slack. Meanwhile, Zulip does what I need and does it well. It scales excellently to large organizations discussing broad arrays of topics. It gets out of my way and I don't find myself thinking about it. In that way it's the perfect tool, because it lets me spend energy focusing on engaging with the conversations rather than wrestling with the interface. I guess I'd describe it as natural and unobtrusive, the sort of thing that does its job so well that you only notice that it's there when something goes wrong and you realize what you've been taking for granted.

Note that my experience is almost exclusively with the web client. My small amount of experience with the mobile app is that it's much less polished.

We used Zulip at $job[-1] and it was awfully painful. I’ve used nearly every chat client invented since the BBS days, and Zulip was one of my least favorite. We’re using Slack now at $job and I vastly prefer it (even though I still call it “IRC”).

The biggest selling points of Zulip, from the POV of the people who put it in place and truly loved it, were that it’s free/OS software, it has explicit threads as a first class citizen, and that it’s very configurable. All those things are true.

The day-to-day use was painful, though. It was riddled with UX problems, e.g., forgetting state between restarts, inconsistent hotkey support, multi-action use paths for common cases, frequent full reloads of its web view. I’d much rather use vanilla IRC than Zulip.

Slack is just enough of a shim layer on IRC, and with good usability. It has threads, and in use it’s not a problem that you can’t name them like Zulip. The integrations are nice to have (e.g., type `/zoom` to start a Zoom meeting) but not a big deal. The UX is clear and predictable and (mostly) stays out of my way.

We use it at our small (15 person) startup. I like that topics are light weight, like git branches, but despite that we struggle to use them effectively (generally dumping thoughts in a select few topics)

One major quirk of the interface is that can be difficult to, at a glance, identify what topic/dm you are actively on, which has lead to a handful of "Oops, what was supposed to be a DM" message deletes.

We use a self-hosted Zulip. It's the first chat system to make everyone reasonably happy -- devs, IT, customer service, and most of the execs.

I used it at a previous job and it was fantastic. The first-class threads are the way chat should work, the UX with the message river is brilliant, the keyboard shortcuts make everything two keystrokes away and it's extremely fast.

In comparison, I hate having to use Slack every day today. It's slow as shit, whenever I type a keystroke too fast (e.g. editing a previous message) it always gets into a weird state (usually edits the message before last and messes up the edits) and it encourages rapid-fire, thoughtless replies. Search also sucks and it's impossible to find anything. I fucking hate Slack.

Love Zulip. Very hackable. Terrific core team who really care.

I briefly used Zulip as part of a friend's community, rather than work. My experience with it was that it's great at first, but when you start to get masses of messages and users, the client becomes laggy and unresponsive. Scrolling through messages particularly sucked because of this.

I'm not sure if it was just our setup, because when I checked the official Zulip web chat, I had the same problem.

We use Zulip at work. I have used Slack in a previous job. Zulip's interface looks a little clunkier than Slack, but I like Zulip.

I liked it a lot, but I'm not an Apple user, and apparently the iOS app was (is?) not great. For me, it's like a vastly better version of NNTP, while slack is more of a slightly improved IRC.