My research group at Stanford uses Zulip for instant messaging. I like it A LOT more than Slack. I'll list a few of the features I think most contribute to why Zulip > Slack (IMHO). Also, I'm not affiliated with the maintainers of Zulip at all. I am just a big fan of their software :).
- Zulip has something called a "topic" which is basically a Slack thread but with a name/subject-line. Unlike Slack threads though, every message you send has to be sent in a topic. Zulip makes it much easy to context switch between these topics too. Ever have a situation in Slack where two people are discussing something in a channel instead of using a thread or DM? That isn't possible in Zulip.
- The Zulip UI offers a lots of nice features compared to Slack too. For one, you can see the number of unread messages in each topic directly from the main page. Zulip also supports multi-line messages so you don't have to send a bunch of message one right after the other to break up text, you can add line breaks directly to your message.
- Zulip has a "message drafts" features which is nice when you want to draft a message (or multiple messages), but will send it later. Zulip will hang onto your drafts until you need it.
- Zulip has full markdown support. You can format links, images, and tables (which are all especially nice when using bots) using standard markdown syntax.
- Zulip has full color syntax highlighting when embedding code-snippets into messages! It has support for basically every programming language I can think of (including brain-fuck!).
- Zulip has support for latex equations in messages.
- Zulip is open-source! You can use the version of Zulip hosted at zulipchat.com or you can deploy your own Zulip server by grabbing the source code from github (https://github.com/zulip/zulip).
- In the time since I have switched from Slack to Zulip (about 1 years ago now), Slack has gone down 3-4 times and has had other connectivity issues; Zulip had maybe 1-2 minor interruptions that I can think of in that time.
- Zulip has something called a "topic" which is basically a Slack thread but with a name/subject-line. Unlike Slack threads though, every message you send has to be sent in a topic. Zulip makes it much easy to context switch between these topics too. Ever have a situation in Slack where two people are discussing something in a channel instead of using a thread or DM? That isn't possible in Zulip.
- The Zulip UI offers a lots of nice features compared to Slack too. For one, you can see the number of unread messages in each topic directly from the main page. Zulip also supports multi-line messages so you don't have to send a bunch of message one right after the other to break up text, you can add line breaks directly to your message.
- Zulip has a "message drafts" features which is nice when you want to draft a message (or multiple messages), but will send it later. Zulip will hang onto your drafts until you need it.
- Zulip has full markdown support. You can format links, images, and tables (which are all especially nice when using bots) using standard markdown syntax.
- Zulip has full color syntax highlighting when embedding code-snippets into messages! It has support for basically every programming language I can think of (including brain-fuck!).
- Zulip has support for latex equations in messages.
- Zulip is open-source! You can use the version of Zulip hosted at zulipchat.com or you can deploy your own Zulip server by grabbing the source code from github (https://github.com/zulip/zulip).
- In the time since I have switched from Slack to Zulip (about 1 years ago now), Slack has gone down 3-4 times and has had other connectivity issues; Zulip had maybe 1-2 minor interruptions that I can think of in that time.