Windows Phone 8.1

Windows Phone 8.1 is the upcoming third generation of Microsoft's Windows Phone mobile operating system, succeeding Windows Phone 8. It was released in preview form to developers on February 10, 2014, and is expected to be released to the general public at Microsoft's Build Conference in San Francisco, California, which will be held from April 2-4, 2014.

All phones currently running Windows Phone 8.0 will be upgradeable to Windows Phone 8.1.

History
Windows Phone 8.1 was first rumored to be "Windows Phone Blue," a series of updates to Microsoft's mobile operating system that would coincide with the release of Windows 8.1. Although Microsoft had originally planned to release WP8.1 during the fall of 2013, general distribution of the new operating system was pushed back until the spring of 2014. Instead of waiting over a year to add new features to Windows Phone 8, Microsoft opted to release three incremental updates to its existing mobile OS. Together, these three updates, which were released in December 2012, July 2013, and October 2013, not only fixed bugs but also added features intended for Windows Phone 8.1, which included the release of DataSense for non-Verizon devices, support for quad-core processors, 1080p high-definition screens of up to six inches, the addition of a "Driving Mode," and extra rows of live tiles for larger "phablet" devices.

The operating system was officially revealed to the public when Microsoft released the Windows Phone 8.1 SDK to developers on February 10, 2014. Within hours of the release, details about the SDK and screenshots were leaked to the public.

Features
Windows Phone 8.1 introduces a host of notable new features, most of which were unveiled in a preview released to developers on February 10.

Web
Windows Phone 8.1 adds a mobile version of Internet Explorer 11 as the default web browser. IE11 carries over many of its desktop counterpart's improvements, which include support for WebGL and normal mapping. A new YouTube web player is also included, with support for HTML5 videos and closed captions.

Multitasking
Building on improvements made in the third update to its predecessor, Windows Phone 8.1 adds support for closing apps by swiping down on them in the multitasking view (invoked by doing a long-press on the "back" button), which is similar to how multitasking operates on iOS. Pressing the back button now suspends an app in the multitasking view instead of closing it.

Multimedia
Xbox Music and Xbox Video provide streaming services for movies, music, and TV shows, and are separated as opposed to being joined together in previous versions. Notably, Xbox Video now has built-in support for video streaming. In addition to separating its music and video streaming services, 8.1 also adds support for separate volume controls, audio and video transcoding, hardware acceleration, stereoscopic 3D, and the ability for apps to capture and record video independently of the operating system's built-in video recorder. Furthermore, built-in support for streaming through DLNA to monitors and television screens, referred to by Microsoft as "PlayTo," is also included, as well as the ability to mirror display from a phone to a separate screen. Media editing tools have also been refined: apps for slow motion video capture, video effects, and audio effects have been added. The stock camera app has been updated with a more minimalist design similar to that of the camera app on Windows 8.1.

Social
Facebook is now included with Windows Phone by default, eliminating the need for users to download the Facebook app separately from the Windows Phone Store. In the preview build of Windows Phone 8.1, the option to add a Facebook account in the "Accounts" section in the Settings menu has been removed, although the reason for its deletion is unknown. Twitter is also more fully integrated into the Contacts Hub.

Notifications and settings
A new notifications center known as "Action Center" has been added, and allows for the ability to change simple settings such as volume controls. The new notifications area's design allows the user to change wireless networks, turn Bluetooth and Airplane Mode on or off, and access "Driving Mode" from four boxes at the top of the screen, while beneath these four horizontally placed boxes include recent text messages and social integration.

Apps can also send users location-specific notifications with the addition of a new geofencing API.

Search
Windows 8.1's universal Bing SmartSearch is now included in Windows Phone 8.1.

Apps
Apps for Windows Phone 8.1 can now be created with the same code as Store apps for Windows 8, and the file extension for WP apps is now APPX (which is used for Windows Store apps), instead of Windows Phone's traditional XAP file format. Applications built for WP8.1 can invoke semantic zoom, as well as access to single sign-in with a Microsoft account. The Windows Phone Store now also updates apps automatically. The store can be manually checked for updates available for applications on a device. It also adds the option to update applications when on Wi-Fi only.

Apps built for Windows Phone 8 and Windows Phone 7 automatically run on Windows Phone 8.1, but apps built for Windows Phone 8.1 will not run on any previous version of Windows Phone.

On-screen buttons
Windows Phone 8.1 includes support for new on-screen buttons that OEMs can use to replace the capacitive "back, "Windows", and "search" buttons that have been required for devices running the OS since 2010. The new on-screen buttons can be hidden by swiping them to the side of the screen.

File system
A new file picker has been added, and SkyDrive has been completely rebranded to OneDrive across the operating system after Microsoft's settlement of a dispute over the "Sky" trademark with BSkyB. Users are also presented with multiple options when a Windows Phone 8.1 device is connected to a computer via USB.

Enterprise and other improvements
Windows Phone 8.1 adds support for VPN, as well as Wi-Fi Direct and Bluetooth 4.0 LE. A new built-in Battery Meter also enables users to check detailed statistics about their device's power consumption and expected battery life.