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Slack to Microsoft: Bundling Teams With Office Is an Antitrust Violation

Microsoft denies any wrongdoing, but the accusation from Slack echoes the antitrust case Microsoft faced two decades ago in the US over bundling Internet Explorer with the Windows operating system.

 & Michael Kan Principal Reporter

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Slack is accusing Microsoft of breaking antitrust law in the European Union by bundling its competing business chat service, Microsoft Teams, with Office, and is calling on European regulators to investigate.

“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,” San Francisco-based Slack said in a statement

Slack's accusation echoes the antitrust case Microsoft faced two decades ago in the US over bundling Internet Explorer with the Windows operating system while giving customers no option to uninstall it. The Justice Department sued in 1998, claiming the bundling helped the tech giant achieve an illegal monopoly in the browser market. 

The case led a US judge to order the breakup of Microsoft. However, the ruling was later overturned for a lesser penalty that only forced the company to open access to its software APIs.

In the EU, regulators also scrutinized Microsoft’s practice of bundling IE into Windows. The effort culminated in an antitrust settlement in 2009 that required the company for five years to offer consumers a choice on the browser they’d like to install when booting up the Windows OS for the first time. 

“We’re asking the EU to be a neutral referee, examine the facts, and enforce the law,” said Slack’s general counsel David Schellhase. “Microsoft is reverting to past behavior. They created a weak, copycat product and tied it to their dominant Office product, force installing it and blocking its removal, a carbon copy of their illegal behavior during the ‘browser wars.’”

Slack says it threatens Microsoft’s lock on enterprise software. But Microsoft says the competition complaint is without merit. According to Redmond, consumers are flocking to Microsoft Teams not due to any bundling, but because the product has strong video conferencing features. 

“We created Teams to combine the ability to collaborate with the ability to connect via video, because that’s what people want,” Microsoft told PCMag in a statement. “With COVID-19, the market has embraced Teams in record numbers while Slack suffered from its absence of video-conferencing. We’re committed to offering customers not only the best of new innovation, but a wide variety of choice in how they purchase and use the product.”

PCMag asked Slack whether it's filing any antitrust action against Microsoft in the US. In response, the company said: “We have ongoing conversations with US policymakers and regulators, and those conversations continue. We’ve talked and will continue to talk with regulators and law-makers in the markets in which we operate.”

On July 27, the CEOs of Amazon, Apple, Facebook, and Google will testify before the House Judiciary Committee during a hearing about competition in the digital marketplace.

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About Our Expert

Michael Kan

Michael Kan

Principal Reporter

My Experience

I've been a journalist for over 15 years. I got my start as a schools and cities reporter in Kansas City and joined PCMag in 2017, where I cover satellite internet services, cybersecurity, PC hardware, and more. I'm currently based in San Francisco, but previously spent over five years in China, covering the country's technology sector.

Since 2020, I've covered the launch and explosive growth of SpaceX's Starlink satellite internet service, writing 600+ stories on availability and feature launches, but also the regulatory battles over the expansion of satellite constellations, fights with rival providers like AST SpaceMobile and Amazon, and the effort to expand into satellite-based mobile service. I've combed through FCC filings for the latest news and driven to remote corners of California to test Starlink's cellular service.

I also cover cyber threats, from ransomware gangs to the emergence of AI-based malware. In 2024 and 2025, the FTC forced Avast to pay consumers $16.5 million for secretly harvesting and selling their personal information to third-party clients, as revealed in my joint investigation with Motherboard.

I also cover the PC graphics card market. Pandemic-era shortages led me to camp out in front of a Best Buy to get an RTX 3000. I'm now following how the AI-driven memory shortage is impacting the entire consumer electronics market. I'm always eager to learn more, so please jump in the comments with feedback and send me tips.

The Best Tech I've Had:

  • My first video game console: a Nintendo Famicom
  • I loved my Sega Saturn despite PlayStation's popularity.
  • The iPod Video I received as a gift in college
  • Xbox 360 FTW
  • The Galaxy Nexus was the first smartphone I was proud to own.
  • The PC desktop I built in 2013, which still works to this day.

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