WhatsApp hits 300 million monthly users and adds voice messaging to app

Smartphone messaging app WhatsApp has added a voice messaging feature to its service.

The development coincides with an announcement that the app now has 300 million monthly active users globally.

WhatsApp currently works across the major smartphone operating systems including iOS, Android, BlackBerry and Windows Phone, and is expected to be released for the freshly-launched Firefox OS soon.

"We are releasing Voice Messages on all of our platforms simultaneously," the company said in a blog post outlining the development.

"We worked very hard to make sure that iPhone and Android devices have perfectly working Voice Messages functionality, and we put extra effort into making sure that BlackBerry, Nokia and Windows Phone users can enjoy the same rich and powerful Voice Messaging experience."

The voice messaging function works in a push-to-talk digital walkie-talkie fashion similar to the Voxer app, which the update will set WhatsApp in direct competition with.

To send a message, users need simply hold down the microphone icon for the duration of the recording. When the icon is released, the message is sent automatically.

Ordinarily, received messages will play out loud through the phone's main speaker when the user presses play. On Windows phones and the iPhone however, when the user holds the device to their head, the app will use the phone's automatic sensors to play the audio from the earpiece speaker, to ensuring private listening.