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Photo: Slack

A war of words (and numbers) between workplace messaging service Slack and Microsoft is heating up, as Slack finds itself having to compete in the category it pioneered.

The big picture: Slack, which went public in June via a direct listing, now finds itself up against Microsoft, which has the luxury of including its rival Teams product as part of its big Office bundle.

By the numbers: While Teams has gained ground — it claims 13 million daily active users — Slack maintains it is still dominant when it comes to what workers are actually using.

  • Last week Slack released statistics showing the company has more than 12 million people actively using its product each day.
  • But it says its users are far more active than Microsoft's, with paid customers connected for an average of 9 hours per day and fully engaged with the service for 90 minutes per day.

What they're saying: In an interview, Slack CTO and cofounder Cal Henderson says Microsoft's numbers really aren't all that impressive when you consider the company has been including Teams in the package for 100 million Office 365 customers for two years now and has been pushing Skype For Business customers over to Teams.

  • "Being at 13 million, I'm not sure that's a success in that context," Henderson said. "People pay for Slack because they see value in it."

Henderson says that Slack's not being part of a big software company's bundle actually gives it a competitive advantage against Microsoft and others. That allows Slack to work as a partner across all the software a business uses, from Microsoft and Google to Salesforce and Workday and startups.

Henderson insists Slack is doing well — even at companies that are big Microsoft Office users.

  • "We've seen some of our fastest growth in Microsoft shops," Henderson said, noting that at least 70% of the company's top 50 customers use Office 365.

What's next: Expect more tough words at Slack's Spec user conference, which kicks off today in San Francisco.

Go deeper

President Joe Biden vows to be "a president for all Americans"

Moments after taking the oath of office, President Joe Biden sought to soothe a nation riven by political divisions and a global pandemic, while warning that "we have far to go" to heal the country and defeat a "virus that silently stalks the the country."

Why it matters: From the same steps that a pro-Trump mob launched an assault on Congress two weeks earlier, the new president paid deference to the endurance of American political institutions.

Updated 39 mins ago - Politics & Policy

Inauguration Day dashboard

U.S. Capitol and stage are lit at sunrise ahead of the inauguration of Joe Biden. Photo: Patrick Semansky - Pool/Getty Images

President Biden has delivered his inaugural address at the Capitol, calling for an end to the politics as total war but warning that "we have far to go" to heal the country.

What's next: Biden and Vice President Harris review readiness of military troops, a long-standing tradition to signify the peaceful transfer of power.

Updated 1 hour ago - Politics & Policy

In photos: The Biden and Harris inauguration

Joe Biden is sworn in as the 46th president of the United States. Photo: Alex Wong/Getty Images

Joe Biden and Kamala Harris were inaugurated as president and vice president respectively in a ceremony at the U.S. Capitol on Wednesday morning.

Why it matters: Top Democrats and Republicans gathered for the peaceful transfer of power only two weeks after an unprecedented siege on the building by Trump supporters to disrupt certification of Biden's victory. Trump did not attend Wednesday's ceremony.