Which version of Windows had the longest support lifecycle?

Among the standard desktop releases listed, Windows XP had the longest support lifecycle. Released in 2001, it received official extended support through April 8, 2014—more than 12 years after its retail launch.

Windows XP’s unusually long life reflected its enormous popularity and its importance to businesses, schools, and hardware manufacturers. Microsoft ended mainstream support in April 2009, but continued security updates during the extended-support period. The operating system’s durability was helped by Service Pack 2 and Service Pack 3, which addressed major security and compatibility issues.

Windows XP was eventually replaced by Windows Vista, but Vista never achieved the same market reach. Windows 7 was also widely adopted, yet its standard support period was shorter. Windows 8.1 and the regular editions of Windows 10 likewise had shorter published lifecycles.

The wording can become complicated when special editions are included. Embedded versions of XP and long-term servicing editions of later Windows releases followed different support schedules. For the conventional consumer and business desktop editions in this quiz, however, Windows XP is the accepted answer.