Windows 9 was not officially released by Microsoft. The confusion often arises due to the existence of Windows 8.1, which was a major update to Windows 8. Microsoft skipped the Windows 9 version and directly moved to Windows 10 in 2015. The decision to skip Windows 9 was part of Microsoft's strategy to streamline its product naming and focus on the Windows 10 platform, which was intended to be a more consistent and unified operating system across different devices.

The rationale behind this decision can be attributed to several factors. Firstly, Microsoft wanted to avoid confusion among consumers and businesses, as the Windows 8 release had faced criticism for its user interface and lack of backward compatibility with legacy software. By skipping Windows 9 and going straight to Windows 10, Microsoft aimed to create a fresh start and emphasize the new features and improvements that Windows 10 offered.

Secondly, the Windows 10 release was timed to coincide with the growing trend of mobile computing and the increasing importance of touch-based interfaces. Windows 10 was designed to be a universal operating system that could run on a wide range of devices, from smartphones and tablets to desktops and laptops. This approach was a significant shift from the device-specific strategies of previous versions.

Data from Statista shows that Windows 10 quickly became the most widely used operating system in the world, surpassing Windows 7 in just a few years. As of 2021, Windows 10 had a global market share of over 70%, making it the clear leader in the operating system market.

In conclusion, Windows 9 was never released by Microsoft, and the company chose to skip this version in favor of Windows 10. This decision was driven by the need to simplify product naming, address consumer and business concerns, and adapt to the evolving landscape of mobile computing. The success of Windows 10, with its high market share, underscores the effectiveness of this strategy.