Google Voice is a voicemail/phone management service by Google launched on March 11, 2009, after acquiring the service GrandCentral.The service provides a U.S. phone number, chosen by the user from available numbers in selected area codes, free of charge to each user account. Users must configure this and/or additional phone numbers that ring simultaneously when their Google Voice number receives a call. For incoming calls, users must have an existing U.S. telephone number to activate their own Google Voice phone number. Inbound calls to the Google Voice number are forwarded to other phone numbers of the subscriber. Received calls may be moved between configured telephones during a call. The user may answer and receive the call on any of the ringing phones or through the web-based app.Users in the U.S. may place outbound calls to domestic and international destinations from their cell phone app or from the web-based application. As of August 2011, users in many other countries also may place outbound calls from the web-based application to domestic and international phone numbers.Many other Google Voice services—such as voicemail, free text messaging, call history, conference calling, call screening, blocking of unwanted calls, and voice transcription to text of voicemail messages—are also available to US residents. In terms of product integration, transcribed and audio voicemails, missed call notifications, and/or text messages can optionally be forwarded to an email account of the user's choice. Additionally, text messages can be sent and received via the familiar email or IM interface by reading and writing text messages in Gmail or by adding contact's phone numbers in Google Talk respectively (PC-to-Phone texting). Google Voice multi-way videoconferencing (with support for document sharing) is now integrated with Google+ Hangouts.The service is configured and maintained by the user in a web-based application, styled after Google's e-mail service, Gmail, or with Android and iOS apps on smart phones or tablets. Google Voice currently provides free PC-to-phone calling within the United States and Canada, and PC-to-PC voice and video calling worldwide between users of the Google+ Hangouts browser plugin (available for Windows, Intel-based Mac OS X, and Linux).Almost all domestic and outbound calls to the United States (including Alaska and Hawaii) and Canada are currently free from the U.S. and Canada, and $0.01 per minute from everywhere else. International calls are billed according to a schedule posted on the Google Voice website.As of October 2009, Google Voice had approximately 1.4 million users, of which 570,000 used the service 7 days a week. This number has risen markedly since Google made the transition of its Google Voice service from ""invitation only"" to be available to all Gmail subscribers in the United States. A Wired Magazine blog post quoted a figure of 3.5 million in 2013.