And in any of those versions, you can make two-way voice and video calls, apply optional two-factor authentication, store up to 10,000 messages, and use up to 5GB of cloud storage per user without forking over any money to Slack. Slack doesn't skimp on the free version: You can get Slack for Windows, Mac, mobile, and within a Web browser. Subscribe to Slack Plus for features like guest access, unlimited message archiving, guaranteed uptime, and increased cloud storage (20GB, versus 5GB in the free version). It's free to use and available for Windows, MacOS, and mobile. Slack is a popular messaging app similar to IRC (Internet Relay Chat) that's oriented toward small-team collaboration.
