On 11 February 2011, Nokia announced a "strategic partnership" with Microsoft, under which it would adopt Windows Phone 7 as its primary operating system on smartphones, and integrate its services and platforms with its own, including Bing as search engine, and integration of Nokia Maps data into Bing Maps. Elop stated that Nokia chose not to use Android because of an apparent inability to "differentiate" its offerings, with critics also noting that his past ties to Microsoft may have also influenced the decision.
On 11 February 2011, Nokia announced a partnership with Microsoft that would see Nokia adopt Windows Phone as its primary smartphone platform, and Symbian would be gradually phased out, together with MeeGo. As a consequence, Symbian's market share fell, and application developers for Symbian dropped out rapidly. Research in June 2011 indicated that over 39% of mobile developers using Symbian at the time of publication was planning to abandon the platform.
By 5 April 2011, Nokia ceased to openly source any portion of the Symbian software and reduced its collaboration to a small group of pre-selected partners in Japan. Source code released under the EPL remains available in third-party repositories.
On 22 June 2011, Nokia made an agreement with Accenture for an outsourcing program. Accenture will provide Symbian-based software development and support services to Nokia through 2016; about 2,800 Nokia employees became Accenture employees as of October 2011
On 1 August 2011, Nokia announced that it would adopt a new three-digit naming system for mobile phone products and stop using letters, effectively ending the Nseries, Eseries, and short-lived Cseries.