Slack

As an application that I use across multiple devices and multiple professional and personal contexts, Slack manages to deliver an effective, efficient, and truly seamless collaborative hub. Not only do we use it here at AlternativeTo, but many companies and both formal and informal working groups use Slack every day to maximize collaborative productivity while minimizing the effort needed to ensure that everyone is on the same page. With the ability to create workspaces that can house seemingly limitless channels, as well as support for plenty of add-ons that can both enhance productivity as well as give you a moment to breathe (such as polling or GIPHY gifs, respectively), Slack can ensure that you're never far from your career or your hobbies.

The UI is consistently unfriendly and getting worse with each change. It's a very busy, brightly colored (toddler friendly color scheme) chat tool with so-so voice chat functions which seems to be progressively getting less stable than Skype for Business (a bar so low that they have to try very hard to be that bad).

They've been introducing more and more "features" to get in the way, such as mandatory channels, the emoji that is mandatory, unprofessional plugins that they encourage you to use, non-chronological order discussions in the same channel, etc. Almost all of this just worked fine if you used their IRC or XMPP gateway. Except -- they're shutting that down precisely because they don't support those features.

The security implications of third party stored communications that you cannot delete are also huge, making it unsafe to use in the enterprise unless you pay for it and have an explicit delete policy.

The company is not responsive to feedback, showing consistent arrogance especially on user accessibility for those who have specific needs like their fonts.