• Slack said on Wednesday that it had filed a complaint against Microsoft with the European Commission over its Teams chat software
  • The complaint accuses Microsoft of engaging in anticompetitive practices by tying its Teams office chat app to its popular Office 356 productivity suite.
  • It comes as major tech firms like Apple, Amazon, Google, and Facebook have been scrutinized over antitrust concerns, which Microsoft has largely dodged until now.
  • Microsoft is Slack's biggest competitor in the work communication software space, and both have grown throughout the Covid-19 pandemic as more people have been working remotely.
  • Visit Business Insider's homepage for more stories.

Workplace communication software maker Slack said on Wednesday that it had filed a competition complaint against Microsoft with the European Commission over its Teams software, a move that comes as tech giants have faced increased scrutiny over their size and influence on the market.

Slack is accusing Microsoft of engaging in anticompetitive practices by tying its Teams chat and collaboration app - which directly competes with Slack - to its popular Office 365 productivity suite.

"We're confident that we win on the merits of our product, but we can't ignore illegal behavior that deprives customers of access to the tools and solutions they want," Jonathan Prince, vice president of communications and policy at Slack, said in a press release. "Slack threatens Microsoft's hold on business email, the cornerstone of Office, which means Slack threatens Microsoft's lock on enterprise software."

The European Commission will have to review Slack's complaint before deciding whether to launch an investigation into Microsoft.

Microsoft's Teams app is Slack's biggest competitor in the workplace communication software space. Both companies have boomed during the coronavirus pandemic as businesses around the world were forced to shift to remote work arrangements. Microsoft said in March that it had added 12 million daily active users for Teams in a single week, while Slack said around the same time that it had added 7 million new paid users since February.

"Teams and Slack are in a fierce battle for market share," Wedbush Securities analyst Dan Ives previously told Business Insider's Paayal Zaveri, adding: "This trend is accelerating and is probably going to continue to accelerate over the coming months as more employees around the world are working remote."

Microsoft was the subject of a historic antitrust battle in the late 1990s, when Judge Thomas Penfield Jackson ruled that its dominance of the PC market deemed it a monopoly. But it has dodged the mounting scrutiny that other large American tech companies like Apple, Amazon, Google, and Facebook have faced in recent years.

The CEOs of these companies are set to testify before Congress about possible antitrust practices on July 27.

Brad Smith, Microsoft's president, has recently been outspoken about the importance of facilitating competition in the tech industry when it comes to app stores. He was recently tapped by the House of Representative's antitrust subcommittee to share his perspective ahead of the July 27 hearing given Microsoft's experience, according to reports from Bloomberg and The Information.

During that conversation, Smith is said to have raised concerns about the way Apple, a Microsoft competitor, manages its App Store. The App Store has come under scrutiny for potentially anticompetitive behaviour.

"The time has come, whether we are talking about DC or Brussels, for a much more focused conversation about the nature of app stores, the rules that are being put in place, the prices and the tolls that are being extracted and whether there is really a justification in antitrust law for everything that has been created," Smith also previously said during a livestreamed Politico event on June 18.

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