Series 40, often shortened as S40, is a software platform and application user interface (UI) software on Nokia's broad range of mid-tier feature phones, as well as on some of the Vertu line of luxury phones. It was one of the world's most widely used mobile phone platforms and found in hundreds of millions of devices. Nokia announced on 25 January 2012 that the company has sold over 1.5 billion Series 40 devices. It was not used for smartphones, with Nokia turning first to Symbian, then in 2012–2017 to Windows Phone, and most recently Android. However, in 2012 and 2013, several Series 40 phones from the Asha line, such as the 308, 309 and 311, were advertised as "smartphones" although they do not actually support smartphone features like multitasking or a fully fledged HTML browser.