On July 22, Slack Technologies announced it had filed a complaint against Microsoft in the European Union, claiming Microsoft is abusing its market dominance to extinguish competition. After reviewing the complaint, the EU will decide whether or not to open an investigation into Microsoft’s practices.

Slack is claiming Microsoft has “illegally tied its Teams product into its market-dominant Office productivity suite, force installing it for millions, blocking its removal and hiding the true cost to enterprise customers.”

Microsoft makes Teams available for no additional charge to many of its Office 365 business customers. Like Slack, it also offers a free version of its group-collaboration product. As of April 2020, Microsoft aid there are 75 million daily active users of Teams. As of late March, Slack said it had 12.5 million simultaneously connected users. Microsoft has nearly 260 million paid seats of Office 365 commercial.

Slack also claims the company “want(s) to be the 2% of your software budget that makes the other 98% more valuable,” while Microsoft “want(s) 100% of your budget every time.” Slack also says Microsoft is repeating its “illegal behavior during the ‘browser wars'” by bundling/tying products.

In May, Slack’s CEO Stewart Butterfield said that Microsoft wasn’t a competitor to Slackj, despite that Slack’s own 10-Q filing cites Microsoft as its main competitor.

I’ve asked Microsoft for comment on Slack’s complaint. No word back so far.