In the information economy, sorting through internal discussions in an organization can be a laborious task, particularly when discussions are conducted through long chains of emails. The goal of the cloud-based team collaboration tool Slack is to simplify internal communication in order to increase efficiency.

This guide to Slack is both an easily digestible introduction to the service, as well as a “living” guide that will be updated periodically to keep IT leaders in the loop on new features, integrations, competitors, and ways in which this technology can be leveraged. This article is also available as a download, Slack: A cheat sheet (free PDF).

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Executive summary

  • What is Slack? Slack is a cloud-based instant messaging tool that is intended to be the center of workplace collaboration, and to integrate with other products your organization uses.
  • Why does Slack matter? Slack attempts to increase productivity by simplifying communication.
  • Who does Slack affect? Practically any group can use Slack, and the free tier has no limit to the number of users that can be added to a group.
  • When did Slack launch? Slack launched in August 2013. Developers continue to improve the service by releasing new features.
  • How do I get Slack? You can create your own Slack team for free. Paid tiers are available with additional features, and education and nonprofit organizations are eligible for discounts.

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What is Slack?

Slack is a cloud-based collaboration tool that aims to be the central platform through which teams communicate. In the most simplistic view, Slack is an email replacement, though it operates more like group messaging or Internet Relay Chat (IRC)–foregoing the formalities of composing emails, and having various channels to which team members can be assigned, rather than the comparatively complex task of managing mailing lists. Additionally, private channels can be used to restrict conversations to pre-approved team members, while public channels are available for team members to join as desired, like IRC.

In contrast to other vendors and established competitors that have a tendency toward vertical integration of features, Slack can integrate with a wide variety of third-party services. Among these are developer tools such as Bitbucket, GitHub, and IFTTT; file storage services such as Google Drive, Box, and Dropbox; project management tools such as JIRA and Zendesk; and social media platforms such as Twitter and Foursquare. An integration also exists for Workday.

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Slack can run in practically any modern browser. Desktop applications are available for Windows, Mac OS, and Linux. Mobile apps are available on Android and iOS. In July 2019, Slack launched a complete rewrite of the Desktop and Web clients to improve start-up times and address memory leaks.

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Why does Slack matter?

The goal of Slack is to increase productivity by simplifying communication, while putting Slack in the middle of your communication workflow. To do so, Slack designers focus on solving problems that users do not know they have–a task so abstract, it is easier to describe in an example than define it.

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Take, for example, the not altogether uncommon task of sending a link to an article via email. The typical greeting and closing and the automatically added signature are extraneous (though polite) components of the purpose of this email, while the task at hand–sending a link–is stuck somewhere in the middle of this text. The link itself needs some amount of context, particularly if the URL has no semantic value. For instance, you would never guess that this page explains enabling two-factor authentication for Apple ID by looking at the URL, or that this YouTube video is a commercial for the soft drink Mitsuya Cider. When you post a link in Slack, it automatically generates a description of the link, reducing the need to provide context for sending a link, and avoiding “risky clicks” for those who do not know what is being linked. This works in a context-dependent way, as well–linking to an article displays the headline, writer byline, and publication name.

Additional features, like the ability to check email and calendars from within Slack through use of the Astrobot plugin (the developer of which has since been acquired by Slack) help workers, save time as they go about their daily tasks. Groups can also share to-do lists, and bots can broadcast notifications programmatically to group members.

Slack features a variety of these helpful utilities. In an interview with CNET, Slack co-founder Stewart Butterfield noted that, “There’s a set of features that people want that they don’t even know that they want… but when they get them, they like them.”

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Who does Slack affect?

Practically any organization–or, generally, a loose association of people–can use Slack. The free tier has no limitations on the number of users that can be added to a group. It retains and indexes the last 10,000 messages for search, file sharing is limited to a 5 GB storage total, and it can utilize 10 third-party or custom apps. Because of this, Slack is gaining momentum as a communication platform outside of work contexts.

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There are additional features available for paid plans. The Standard plan, which is $6.67 user/month, billed annually, stores unlimited messages, and can use an unlimited number of integrations. It also includes custom retention policies, user groups, Google Authentication/Apps for Domains sign-in, guest access, and a configurable email ingestion service. For most midsize organizations, the Standard plan should be adequate. The Plus plan, at $12.50 user/month billed annually, includes SAML-based single sign-on, and compliance exports of message history, and real-time Active Directory sync. Slack’s Enterprise Grid plan, targeted toward organizations with between 500 and 500,000 employees, allows for unlimited workspaces and shared channels, enabling organizations to set up Slack in a way that better mirrors their organizational structure.

Organizations that require an extensive level of collaboration between group members can benefit from adopting Slack. Programmers, journalists, and other professions that are likely to be spread across different offices, employ a high number of remote and/or freelance workers, or have group members that travel often stand to gain the most from adopting Slack. Conversely, extremely client-focused businesses such as a medical practice or a real estate agency are less likely to need Slack, as more communication is done with the customer than within the organization.

Slack’s survey results provide an interesting look at how organizations have changed after adopting Slack. According to the company, the number of emails generated by groups that adopted Slack was reduced by an average of 48.6%, while meetings were reduced by an average of 25.1%. Respondents (80.4%) also indicated that the use of Slack increased transparency.

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When did Slack launch?

Slack was originally developed as an internal communication tool for the team working on the computer game “Glitch” (which has been forked as Eleven). While the plans for that game did not meet expectations, Slack held more promise as a product and publicly launched in August 2013. Since then, the developers have been actively soliciting feedback and implementing new features based on user requests.

Since launch, Slack added support for voice and video calls, with users on the free tier limited to 1:1 calling. Paid tiers can have group calls with up to 15 people. If you prefer not to use Slack’s internal implementation, it is (and will continue to be) possible to use Skype integration instead. As part of the focus on workgroup collaboration, Slack has increased the granularity of control available to group administrators, as well as added support for screen sharing in video calls.

As of September 2019, Slack has 10 million daily active users across the platform, with more than 100,00 paid teams. Previously, Slack indicated that 200,000 developers are building applications for use with Slack.

Slack is the frequent subject of acquisition rumors. In March 2016, it was rumored that Microsoft was preparing an $8 billion offer for the company, though this was apparently vetoed by Satya Nadella and Bill Gates. In June 2017, it was rumored that Amazon had an interest in purchasing Slack Technologies at an estimated price tag of $9 billion. Slack completed Series H funding in August 2018, bringing it to a valuation of $7.1 billion. Slack surged to a $23 billion valuation following its IPO on June 20, 2019.

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What services compete with Slack?

Microsoft’s Teams platform is the primary competitor against Slack. Teams launched on March 14, 2017, to largely negative criticism, as using Teams required subscriptions to Office 365 — a service which (at the time) started at $60 per user per year, and cost $240 per user per year if the full selection of Office apps is included. Further, it was not initially possible to add people outside of an organization, leading ZDNet’s Ed Bott to declare that for “small businesses, freelancers, and agile organizations, it’s a non-starter.” Microsoft added this feature a year later. Microsoft introduced a free tier of Teams in July 2018, to compete head-to-head with Slack’s freemium model.

Of note, Microsoft’s “Skype for Business” application (which was called Microsoft Lync from 2011-2015, and Microsoft Office Communicator from 2007-2010) was replaced with Teams. Likewise, Microsoft Classroom has also been replaced with Teams. Despite these products being replaced with Teams, Yammer, which was acquired by Microsoft in 2012 for $1.2 billion, has not yet been discontinued.

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The independent competitor Twist bills itself as a “communication tool for teams who believe there’s more to work than keeping up with group chat apps.” It has an intentionally minimalist approach, as it lacks an online status indicator. A free tier exists, with message retention limited to one month. The unlimited tier is available for $5 per user, per month.

Open source alternatives to Slack also exist. The most popular of these is the Matrix project, which can be tried for free at

Atlassian’s HipChat and Stride messaging platforms were the biggest Slack competitors, though in July 2018, the company announced that they would be discontinued, with existing workspaces migrated to Slack.

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How do I get Slack?

You can create your team for free to start evaluating the platform. For qualifying educational institutions, Slack offers discounts of 85% from the annual price of the Standard and Plus plans. For nonprofit organizations, Slack offers free access to the Standard plan.

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How do I use Slack?

Slack does not have a particularly steep learning curve, though some features that greatly increase usability can be difficult to surface, due to unclear user interface cues. While individual messages can be starred (similar to Gmail, in order to save them for easy future access), there is a difference between starred items and starred contacts–to keep a channel or direct message from disappearing from the sidebar, you can star the currently open channel or direct message by clicking the tiny star outline under their name at the top of the window.

For more how-tos on getting started with Slack, check out the links below.

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Image: Slack