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. S40 has more features than the Series 30 platform, which is more basic. They are not used for smartphones, in which Nokia primarily uses Windows Phone, and up until 2012 Symbian. However, in 2012 and 2013, several Series 40 phones from the Asha line, such as the 308, 309 and 311, have been advertised as "smartphones" although they do not actually support smartphone features like multitasking or a fully fledged HTML browser.
In 2014, Microsoft acquired Nokia's mobile phones business. As part of a licensing agreement with the company, Microsoft Mobile is allowed to use the Nokia brand on feature phones, such as the Series 40 range. However, a July 2014 company memo revealed that Microsoft would end future production of Nokia's feature phone lines in favor of Windows Phone.
Series 40 was officially introduced in 1999 with the release of the Nokia 7110. It had a 96 × 65 pixel monochrome display and was the first phone to come with a WAP browser. Over the years, the S40 UI has evolved from a low resolution UI to a high resolution color UI with an enhanced graphical look. The third generation of Series 40 that became available in 2005 introduced support for devices with resolutions as high as QVGA (240×320). It is possible to customize the look-and-feel of the UI via comprehensive themes. In 2012, Nokia Asha mobile phones 200/201/210, 302/306/305/308/310/311, 303 and 311 were released and all used Series 40.
It provides communication applications such as telephone, internet telephony (VoIP), messaging, email client with POP3 and IMAP4 capabilities and Web browser; media applications such as camera, video recorder, music/video player and FM radio; and phonebook and other personal information management (PIM) applications such as calendar and tasks. Basic file management, like in Series 60, is provided in the Applications and Gallery folders and subfolders. Gallery is also the default location for files transferred over Bluetooth to be placed. User-installed applications on Series 40 are generally mobile Java applications. Flash Lite applications are also supported, but mostly used for screensavers.
Support for SyncML synchronization with external services of the address book, calendar and notes is present. However, with many S40 phones, these synchronization settings must be sent via an OTA text message.
Series 40 is an embedded software platform that is open for software development via standard or de facto content and application development technologies. It supports JavaMIDlets, i.e. Java MIDP and CLDC technology, which provide location, communication, messaging, media, and graphics capabilities. S40 also supports Flash Lite applications.