Slack

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.

Strengths
• Easy user interface
• Facilitate team communication & work

Challenges
• Potentially not secure. Because the code is not available publicly. So it can not be review by the public. In other words, there is a risk of abuse.

• It is own by a for-profit corporation. It is not owned by a not-for-profit community. Usually a corporation first priority is to hoard money. Not serve you and protect your privacy.
Slack software code is not open source. This means it is less secure than alternative open source software. Slack is owned by the for profit corporation Slack Technologies, Inc. Source at
https://gwhois.org/slack-edge.com+dns
Slack Technologies, Inc. are located at
155 5th Street, 6th Floor
San Francisco, CA, 94103, USA

If you need stronger security, you might be interested to consider another software with the code fully publicly available for review. Such as Mattermost at https://about.mattermost.com
Related page at Mattermost

• Slack often advertise and offer feature for free, then after you start using it for a while, they either stop offering that free feature, then you have to pay to continue using it, or they fully stop offering the feature. And offer you to use their other paid feature. Such as gateways. From Slack start until May 15th 2018, Slack gateways were allowing you to connect and interact with Slack. Using protocols such as the community-owned code, free, distributed and federated protocols IRC and XMPP clients. Now Slack no longer allow those protocol to connect and ended Slack gateways. Instead they invite you to use their corporate owned and paid Slack’s protocols. Why? Maybe to monetize and attach strings to you? ;) Sources:
https://archive.fo/8Lh3t
https://archive.fo/LXdBQ

• Exporting your data might be useless or mostly useless. Because Slack increasingly stop supporting community-owned code, free, distributed and federated protocols and standard. In other words, yes you can export some of your data, but it can not or some of it can not be imported easily and quickly into another provider of your choosing. Also the free Slack plan can only export links to files. In other words, you can NOT export your files. So you loose those when you close your Slack account. To export your files you have to pay for Slack “Plus plan”. Again to monetize and attach more strings to you? ;) Source at https://archive.fo/QP17R

[Edited by Francewhoa, April 19]

8$ per user monthly, its so expensive, I prefer to use Ziggs.io because its free and has much more features.

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.

Integrates with so many other useful apps and bots. It's a winner.