I use Zulip because of the threading model i.e. having topics inside a channel makes it easy to catch up to topics and keeps your organisation's chat well organised.

1.) Having topics inside a channels ensures that you can have multiple conversations in the same channel at the same time. For e.g. Imagine a chat system with no topics and only channels. A real-time conversation about say an expensive migration is going in the #backend channel. But you have a question about how the push notifications work in the project. In that case you will either hesitate to post your question (which would be the mostly likely outcome if you're a new member especially) or you would interrupt/disturb the ongoing conversation and both of the conversations would go on in parallel in the same stream in a convoluted and incoherent manner.

Having topics inside channels in Zulip in the above situation allows you to just create a new topic inside the #backend channel and initiate your conversation there without worrying about the other conversations happening in the same channel at the same time.

2.) Having topics defined for each conversation makes you finding old conversations more convenient and faster. In a chat system with no topics inside channels, you would have to search the entire text content with the exact text that you typed say maybe 6 months ago which you may or may not remember exactly as is.

While just having a look at the topic list in Zulip chat in the above case would return you the conversation about the topic you were looking for without searching the entire text. This makes searching easier and faster. Please do note that a search across the entire text is also much faster in Zulip than its competitors like slack.

3.) Each conversation is linkable which is super convenient i.e. you can get a link to a conversation like https://chat.zulip.org/#narrow/stream/7-test-here/subject/My.20Test.20Topic/near/666741 and share it.

4.) The topic list for a channel in Zulip also acts as a summary of the conversations that happened in the channel. For a person who has been inactive in an organization for a long time, the topic list make its easier to catch up to your messages missed in the past.

Zulip has easily the best threading model among all the chat applications and I prefer it over Slack, Mattermost, RocketChat, Hipchat, Discord etc. Each and every conversation is a seperate thread and has a topic. This model makes it extremely easier to catch up and participate in conversations. Once you get used to the threading model of Zulip its hard to tolerate threading model like Slack which is really inefficient and time wasting.

I use Zulip instead of Slack, Mattermost, or RocketChat because of its first class threading. One week after switching to Gmail (in 2004) I realized I was never (willingly) going to use an unthreaded email product again. I had that same experience the first time I saw Zulip.

Zulip is also fully open-source, with a well-maintained (e.g. 90+% test coverage, fully static python), easily extensible code-base. In many companies, your communication platform (chat or email) is the center of the workplace -- no one asks for a chat integration into their calendar, they ask for a calendar integration into their chat. A fully open-source codebase means you can customize Zulip to your needs, and are never at the whim of a corporate maintainer who can't or won't fix simple bugs, or who will charge you tens of thousands of dollars for making minor customizations.

I use Zulip because I love how it lets me focus on my work, and doesn't need me to be constantly online to be able to participate in conversations that matter to me. Zulip's topics make it super easy to get an overview of all the conversations that happened while I was away, and pick and choose the conversations that I want to catch-up with. Slack 's threads seem like an after-thought and aren't effective for catching-up at all!

I also love the Zulip community, and the care and effort put in by the members to make it a friendly and welcoming community to new developers, and to make the contribution experience pleasant for all the contributors.

I use Zulip because it has let us build our community, and scaled with us. Our open community has 1000s of members and I cannot imagine what other IM software would begin to support us. In particular, the stream/topic model has let us scale further, along with seamless signup, multi-platform availability, and the right prices. Also, because the development team is so active and fixes issues in a timely fashion.

Slack is the industry standard for managed instant messaging (IM). A good alternative would be to self (or cloud) host an open source IM such as Mattermost but as always it would be a good idea to do a cost benefit analysis between the solutions.

Some of the main things to consider:

• Having a good SDK for plugin creation
• Having good integrations with existing tools ( JIRA , GitHub , OpsGenie , etc.)
• Cost
• Maintenance and administration
• Covers all your businesses use cases

I use Slack because it offers the best experience, even on the free tier (which we're still using). As a comparison, I have had in depth experience with HipChat, Stride, Skype, Google Chat (the new service), Google Hangouts (the old service). For self hosted, Mattermost is open source and claims to support most Slack integrations, but I have not extensively investigated this claim.

We run a major community project named as @Donut which is an #OpenSource social platform which allows communities to set up their own social environment and @slack platform drives us through the best experience of community interaction. Though we have been using some Open Source Interacting platforms like Gitter and Zulip but the fact that Slack exists and is such an essential tool, it’s really helped us with scaling and still feeling connected to one another across remote places with various teams with appropriate features in it.

The #User-Friendly Slack brings all the organised conversations at one place giving a prospectus to feel the better user experience on desktop.

Followings its pros:

• Allow creating of various channels which can be best suited to organised #projects, #teams and #events.
• Allow multiple tools and integrations such as Google Drive and GitHub
• Video Conferencing addition helps teams to organise meetings.
• No limit for addition of users and its free.
• Allow threads to keep side conversations from derailing the topic or project at hand.

The most crucial thing it supports the best security and protection with 2 factors authentication.