Slack is a cloud-based team communication tool founded by Stewart Butterfield in 2013. Slack offers chat rooms, private groups, direct messaging, and file sharing. It's also frequently augmented with bots and apps through its API. Slack is available as a web app, and also runs on iOS, Android, macOS, Windows, and Linux. We cover major changes and updates to Slack, which has become the leading tool of its kind in the industry, and the rising competition from companies such as Facebook and Microsoft.