Slack

Slack isn't worried about Microsoft's big Teams push - The Verge

https://www.theverge.com/2019/7/16/.../slack-microsoft-teams-competition-comparison... - Microsoft revealed last week that it now has more than 13 million people using its Microsoft Teams chat software, a milestone that means the app has overtaken Slack. ... Microsoft has been leveraging its popular Office 365 service to bundle Microsoft Teams into its offering ...

If Slack is so good, why are so many companies trying to fix it?
https://www.vox.com/2019/6/24/18691757/slack-ipo-competitors-apps
"The platform also faces competition from tech behemoths — Google G Suite, Microsoft Teams, and Facebook Workplace all share and expand on Slack’s basic premise.