Launched in August 2013 by co-founders Stewart Butterfield, Eric Costello, Cal Henderson and Serguei Mourachov, Slack is a team communication tool that provides real-time messaging, archiving and search capabilities. Slack offers private groups, direct messaging and persistent chat rooms organized by topic. All content is searchable from one search box. Slack integrates with many third-party services and supports community-built integrations. Slack provides apps for Mac, iOS, Android and Windows, a Web version, and an unofficial client for Linux.