Facebook's Workplace business software has grown by about 40 percent in a year to reach seven million paying subscribers as the pandemic accelerated a remote work trend, the company said Tuesday.

The service, which companies can use as an internal social network to communicate with employees, still trails behind top rivals like Teams which Microsoft says now has some 145 million daily active users.

Facebook said it has notched up some big users like Starbucks coffee chain and the World Health Organization.

"We built Workplace as an internal version of Facebook to run our own company, and it was so useful we started letting other organizations use it too," Facebook chief Mark Zuckerberg said in a post.

From about a year ago the number of paid subscribers has grown by 40 percent, he added.

As the pandemic closed offices due to health risks, companies shifted to having employees tend to jobs online when possible.

Use of video and collaboration platforms hosted by companies including Zoom, Slack, Microsoft, and Google rocketed.

As some firms plot returns to office life, it is likely that "hybrid" work models that mix remote and on-site work will become a norm at businesses.