While Microsoft's investments in the platform were headlined by a major partnership with Nokia (whose Lumia series of smartphones, including the Lumia 520 in particular, would represent the majority of Windows Phone devices sold by 2013)[13] and Microsoft's eventual acquisition of the company's mobile device business for just over US$7 billion (which included Nokia's then-CEO Stephen Elop joining Microsoft to lead its in-house mobile division), the duopoly of Android and iPhone remained the dominant platforms for smartphones, and interest in Windows Phone from app developers began to diminish by mid-decade.

Larry Lieberman, senior product manager for Microsoft's Mobile Developer Experience, told eWeek: "If we'd had more time and resources, we may have been able to do something in terms of backward compatibility.

"[23] Lieberman said that Microsoft was attempting to look at the mobile phone market in a new way, with the end user in mind as well as the enterprise network.

[26] The event focused largely on setting up "a new global mobile ecosystem", suggesting competition with Android and iOS with the words "It is now a three horse race".

[30] Jo Harlow, whom Elop tapped to run Nokia's smartphone business, rearranged her team to match the structure led by Microsoft's VP of Windows Phone, Terry Myerson.

[32][33] At the Consumer Electronics Show in 2012 Nokia announced the Lumia 900, featuring a 4.3-inch AMOLED ClearBlack display, a 1.4 GHz processor and 16 GB of storage.

[39] Windows Phone 7 was announced at Mobile World Congress in Barcelona, Catalonia, Spain, on February 15, 2010, and released publicly on November 8, 2010 in the United States.

[45] A minor update released in 2012 known as "Tango", along with other bug fixes, lowered the hardware requirements to allow for devices with 800 MHz CPUs and 256 MB of RAM to run Windows Phone.

[48][49][50] New features added include a notification center, support for the Internet Explorer 11 web browser, with tab syncing among Windows 8.1 devices, separate volume controls, and the option to skin and add a third column of live tiles to the Start Screen.

Cortana replaced the previous Bing search feature, and was released as a beta in the United States in the first half of 2014, before expanding to other countries in early 2015.

[59][60][61] When connected to an external display, devices could also render a stripped-down desktop interface similar to Windows on PCs, with support for keyboard and mouse input.

[74] The default Windows Phone user interface has a dark theme that prolongs battery life on OLED screens as fully black pixels do not emit light.

The image is visible through the transparent area of the tiles and features a parallax effect when scrolling which gives an illusion of depth.

Users input text by using an on-screen virtual keyboard, which has a dedicated key for inserting emoticons,[78] and features spell checking[78] and word prediction.

Windows Phone 8.1 introduces a new method of typing by swiping through the keyboard without lifting the finger, in a manner similar to Swype and SwiftKey.

Here, information from each of the contacts is combined into a single page which can be accessed directly from the Hub or pinned to the Start screen.

[85] The two hubs were previously combined until standalone apps were released in late 2013, shortly before Windows Phone 8.1 debuted.

It has also been previously reported that the DivX and Xvid codecs within the AVI file format are also playable on WP devices.

[89][90] Windows Phone does not support DRM protected media files that are obtained from services other than Xbox Music Pass.

Users also have the ability to use a "Tap and Send" feature that allows for file transfer between Windows phones, and NFC-compatible devices through NFC.

Microsoft's General Manager for Strategy and Business Development, Kostas Mallios, said that Windows Phone will be an "ad-serving machine", pushing advertising and brand-related content to the user.

These hardware partners were later joined by Acer, Alcatel, Fujitsu, Toshiba, Nokia, and Chinese OEM ZTE.

[122] Sony (under the Xperia or Vaio brand) had also stated its intention to produce Windows Phone devices in the near future.

[123] Yezz announced two smartphones in May, and at Computex 2014 BYD, Compal, Pegatron, Quanta and Wistron were also named as new Windows Phone OEMs.

[125] The Metro UI and overall interface of the OS were highly praised for their style, with ZDNet noting their originality and fresh, clean look.

[126] Engadget and ZDNet applauded the integration of Facebook into the People Hub as well as other built-in capabilities, such as Windows Live, etc.

However, in version 8.1, the once tight Facebook and Twitter integration was removed, so updates from those social media sites had to be accessed via their respective apps.

[136] In mid-2012, IDC had suggested that Windows Phone might surpass the faltering BlackBerry platform and potentially even Apple iOS because of Nokia’s dominance in emerging markets like Asia, Latin America, and Africa, as the iPhone was considered too expensive for most of these regions and BlackBerry OS was possibly going to feature a similar fate as Symbian.

[140] As of the third quarter of 2013, Gartner reported that Windows Phone holds a worldwide market share of 3.6%, up 123% from the same period in 2012 and outpacing Android's rate of growth.

[145] In August 2017, the New York Police Department ordered Apple iPhone products to replace its deployment of 36,000 Lumia 830 and Lumia 640 XL Windows Phone devices, partly citing Microsoft's end of support for Windows Phone 8.1 on July 11, 2017, and its minuscule market share.