The private testing period has expired for the Windows Phone version of BlackBerry's free messenger app and now all users of Microsoft's mobile platform have access to beta version of the app.

The BlackBerry Messenger (BBM) app had already been released on Android and iOS before the invite-only beta even began on Windows Phone, but there has been a large enough demand for the app to finally bring it to Microsoft's small, but growing, mobile platform.

"As the popularity of BBM continues to grow, we are thrilled to have the opportunity to expand its availability to the Windows Phone community," said John Sims, president of global enterprise services at BlackBerry. "The BBM app for Windows Phone shows our commitment to supporting cross-platform capabilities, and we are excited to be working with Microsoft to deliver a new level of collaboration to the Windows Phone platform."

BlackBerry said it has reworked BBM to give it a look and feel of a native app on Windows Phone. The app was simplified to focus on contacts, chats and information feeds.

The Contacts section unifies all of a user's contacts into a single pool -- contacts can even be pinned to the Start screens on Windows Phone devices. There's also a multiselect feature that allows BBM users to start chats with a group of contacts.

The Chats section allows for returning to conversations, starting new ones or broadcasting multimedia messages to other individuals.

The Feeds section adds a social networking element to BBM, allowing users to post and view status updates like on Facebook -- users can comment on status updates by simply touching a contact's name. Other social elements on BBM include an invite option and a suggestions algorithm that suggest new contacts to add.

"We are intent on bringing the most popular application experiences to Windows Phone, and with BBM, we are pleased to bring many of its top features to the Windows Phone platform," said Bryan Biniak, vice president and general manager of developer experience at Microsoft. "BBM on Windows Phone brings our customers the secure, easy-to-use messaging experience they demand, and we expect that new features will roll out in the months to come."

While Windows Phone had to wait in line behind iOS and Android for BBM, the apps developers were pleased enough with the enhancements they brought to Microsoft's mobile platform that they hinted the overhauled elements would be rolled out on Apple and Google's mobile operating systems.

The beta version of BBM was compatible with both Windows Phone 8 and 8.1 and, along with Cortana, could help the platform's small user base continue its solid growth.