The free version of Microsoft Teams. (Microsoft Photo)

Microsoft Teams now has more than 20 million daily active users, a 50 percent spike in four months that puts the tool well ahead of its chief rival Slack.

Microsoft revealed the number of Teams users for the first time in July, about a year after it first started offering a free version of the service. Teams has the advantage of being part of the Microsoft 365 ecosystem with a pool of millions of users to pull from, setting it up for rapid growth.

Slack stock is down more than 9 percent as of mid-morning Tuesday.

Last month, Slack said it had more than 12 million daily users, a 37 percent increase over the prior year. Despite trailing Microsoft in the number of users, Slack has said its high level engagement — the average paid customer spends 9 hours a day on Slack and more than 90 minutes actively using it — gives it an advantage in shaping the future of work.

Update: Here’s a statement from Slack:

“As we’ve said before, you can’t transform a workplace if people aren’t actually using your product. Slack continues to see unmatched engagement on our platform with 5+ billion weekly actions, including 1+ billion mobile actions. Among our paid customers, users spend more than 9 hours per workday connected to our service, including spending about 90 minutes per workday actively using Slack.”

The two companies are in the midst of a fierce, multi-year rivalry for dominance of the competitive market for chat-based collaboration tools, which also includes tech giants Google and Facebook. Microsoft and Slack have been aggressive in making splashy announcements this year to showcase the growth of their platforms.

Microsoft today shared findings of a new study with international design and consulting firm IDEO to determine the common traits of successful teams. The Art of Teamwork study looked at a variety of different professions — including astronauts, chefs, television producers, and nurses — to figure out best practices that Microsoft could also adapt to Teams as it continues to grow rapidly.

Here are the traits they came up with and a description from Microsoft and IDEO:

  • Team Purpose: “Keeps teams focused, fulfilled, and aligned on achieving their objectives.”
  • Collective Identity: “Fosters a sense of belonging and helps team members work together as a unit.”
  • Awareness and Inclusion: “Enables teams to navigate interpersonal dynamics and value everyone’s perspective.”
  • Trust and Vulnerability: “Encourages interpersonal risk-taking in teams.”
  • Constructive Tension: “Serves as a generative force for new ideas, driving better outcomes.”

The rivalry between Slack and Microsoft is well-documented. It dates back to the launch of Teams in 2017 when Slack took the unusual step of placing a full-page ad in The New York Times both congratulating the tech giant and warning that “all this is harder than it looks.”

Since then, Microsoft has acknowledged Slack as a major competitor in its annual report. And the Redmond, Wash. tech giant even included the tool on a list of software that Microsoft employees are discouraged or prohibited from using, primarily for security reasons.

Slack acknowledged the uphill battle it faces against larger competitors, specifically Microsoft, as a significant risk to the company going forward.

In recent weeks, the CEOs of both companies have bragged about their respective collaboration tools.

survey of IT pros late last year found that Teams passed Slack in usage and trailed only Skype for Business, another Microsoft product. The company plans to replace Skype for Business as its primary meeting tool with Teams, which could speed up growth even further.

Like what you're reading? Subscribe to GeekWire's free newsletters to catch every headline

Job Listings on GeekWork

Find more jobs on GeekWork. Employers, post a job here.