Previously, businesses without Office 365 subscriptions that have wanted to try out Teams have been limited to a month-long trial. The free version of the product is intended to make it easy for potential customers, typically teams of workers and small businesses, to start using Microsoft's products and become embedded in them.

The new version is available for groups of up to 300 people and gives users unlimited messages and search, as well as 10 gigabytes of data storage, plus 2 gigabytes more for each team member, Microsoft said.

While the free version of Teams will not offer the same functionality as the Office 365 version, it will include some features not offered in the free versions of Slack that could lure prospective customers.

Users of the free version of Teams can also upgrade to paid Office 365 plans, which gets them more storage and access to more of Microsoft's cloud-based Office apps, and Microsoft is hoping at least some of them do.

Microsoft has been competing with Slack since introducing Teams in early 2017. The product is used by 200,000 organizations, the company said in March. Slack in May said that Slack is used by 70,000 paying organizations.

Slack, Microsoft and companies including Google, Cisco Systems , Facebook and Atlassian Corp PLC have launched products in the fast-growing workplace collaboration market.

Ahead of the Teams announcement, Slack on Tuesday announced improvements to its own chat app's search features that the startup said will make it easier for users to find messages. The improved search features apply to all versions of Slack and will roll out to users in the coming weeks, the company said.