What just happened? Microsoft has gone on the offensive by offering a complementary version of Teams. How long will it take for Slack to sweeten its free tier? Not long, we suspect.

Microsoft introduced Teams in late 2016 as an alternative to Slack, the popular team collaboration tool. Since that time, Teams has been adopted by more than 200,000 businesses around the globe but hasn't appealed to small outfits and freelancers due to a lack of a free version. Today, that changes.

On Thursday, Microsoft launched a free version of Teams worldwide across 40 languages. It supports up to 300 users and offers unlimited app integrations and search, features you won't find in the free version of Slack.

The free version of Teams also includes unlimited chat messages, built-in audio and video calling for individuals and groups as well as 10GB of team file storage plus 2GB of personal storage per user. Microsoft's offering additionally boasts guest access.

By comparison, the free version of Slack is limited to 10 app integrations, 5GB of file storage and doesn't permit guest access.

There will still be incentive for some users and businesses to pony up for the paid version of Teams. It's the way to go if you want full integration with Office apps like Word and Excel, need more storage or require other Microsoft services like SharePoint, OneDrive or Yammer. Pricing starts at $5 per month.