FILE PHOTO: The Microsoft logo is shown on the Microsoft Theatre at the E3 2017 Electronic Entertainment Expo in Los Angeles, California, U.S. June 13, 2017. REUTERS/ Mike Blake

(Reuters) - Microsoft Corp MSFT.O said on Tuesday its workplace messaging app, Teams, has more than 20 million daily active users, up from 13 million in July.

The software maker offers the app as part of some Office365 business packages, as well as a free version. Teams allows users to chat, share files, make calls and hold web video conferences.

Microsoft Teams, used by companies such as General Electric GE.N and SAP SAPG.DE, competes with Slack Technologies Inc WORK.N.

Slack, whose customers include Electronic Arts Inc EA.O and Nordstrom Inc JWN.N, reported more than 10 million daily active users in the second quarter ended July 31.

Slack’s shares fell 8.4% following the news, to $21.18. They are down 45% from the close of their first day of trade in June.

Microsoft Teams also competes with Workplace by Facebook Inc FB.O and Cisco Systems Inc's CSCO.O Webex Teams.