Atlassian, a team collaboration software provider, is set to acquire productivity app maker Trello for $425 million.

The app has amassed more than 19 million registered users in the five years since it launched, and is used in more than 100 countries.

The acquisition will “expand Atlassian’s leadership in powering all types of teamwork”.

“Atlassian knows more about how teams work than any company on the planet, which is why our collaboration suite powers teams of all shapes and sizes, from bleeding-edge startups to the Fortune 50,” said Mike Cannon-Brookes, co-founder and co-CEO.

He explained that Trello has built an “incredibly sticky and useful” product and that the addition of Trello “will be a great complement to our existing portfolio of team collaboration software as we look to reach 1 billion knowledge workers globally”.

Trello’s users include the United Nations, Google, Fender Music and National Geographic.

Michael Pryor, Trello’s CEO, said: “Atlassian’s deep investments in research and development will help augment Trello’s product offering. And the broader team collaboration portfolio Trello will integrate with will let us help customers in new and exciting ways.”

According to Wired, Trello was the fourth-most popular project management tool tracked by Project Management Zone, and the fastest growing tool in 2016.

It also quoted an analyst at 451 Research as saying that the business communication and collaboration software market will grow from $15 billion in 2016 to more than $28 billion in 2020.

The transaction is expected to close in the third quarter of fiscal 2017, subject to closing conditions and regulatory clearance.