This is probably why Microsoft has been aggressively pushing users to upgrade to Windows 11 after the previous version of the OS loses support -- so that its users would install the latest version of Windows on their current system (or get a new PC if their system is incapable of running the latest version). Although macOS is a threat to Windows, especially with the launch of Apple Silicon, we cannot say that those 400 million users all went and bought a MacBook. That's because, as far back as 2023, Mac sales have also been dropping, with Statista the computer line, once holding more than 85% of the company revenue, now making up just 7.7%. The shrinking Windows user base can be attributed to a combination of factors -- a major one being the global move toward a mobile-first world, where smartphones and tablets are increasingly replacing traditional PCs for everyday computing needs., Windows seemingly lost 400 million users in the past three years — official Microsoft statements show hints of a shrinking user base, Microsoft's active Windows device count has reportedly dropped by 400 million in three years, from 1.4 billion (2022) to just over 1 billion, signaling a shrinking user base..