Windows 11 is looking toward artificial intelligence, agents, and a new generation of PCs, but a core part of how it works still rests on a foundation created more than three decades ago: Win32. Mark Russinovich, CTO of Microsoft Azure and creator of Sysinternals, has reminded people of a paradox that sums up Microsoft’s operating system rather well: those who lived through computing in the 1990s may have expected flying cars and moon stations by 2026, not Win32 still being a central part of Windows.
That may sound strange, even uncomfortable, to those who associate old technology with obsolete technology. But in operating systems, age is not always a flaw. Sometimes it is an advantage. Win32 is not still there out of nostalgia, but because it supports a vast amount of applications, professional tools, drivers, enterprise utilities, industrial software, administration tools, and workflows that millions of users and companies still need every day.
Win32 is not just the past: it is compatibility
Win32 is an application programming interface, an API, that allows developers to create desktop applications for Windows. Microsoft still documents it as one of the available platforms for building native Windows software, especially with C++ and direct access to operating system capabilities.
Its importance is not only explained by what it meant for Windows 95, Windows NT, or Windows XP. It is explained by what it still enables today: an application written years ago can continue to run, a company does not have to rewrite all its internal software at once, and critical tools can keep operating even though the operating system has changed its appearance, security model, driver architecture, app store strategy, or cloud integration.
Backward compatibility has been one of Windows’ greatest strengths. It has also been one of its greatest burdens. Every new decision has to coexist with decades of existing software. Change too much and applications break. Change too little and modernization slows down. Microsoft has spent years trying to balance those two forces, sometimes successfully and sometimes in ways that have confused both developers and users.
Microsoft’s own ecosystem proves it. UWP is still supported, but the company presents WinUI and the Windows App SDK as the preferred path for building modern applications. Windows App SDK provides APIs and tools for modern desktop apps and can be integrated with WinUI 3, WPF, Windows Forms, or Win32. In other words, even the modern path does not completely break with legacy: it tries to wrap it, extend it, and make it coexist with new layers.
The problem is not old code, but how it is maintained
The presence of 1990s technology in Windows 11 should not be interpreted as an admission of failure. All major systems carry old layers. Linux retains historical decisions, macOS still carries Unix and NeXTSTEP heritage, and much of the Internet runs on protocols designed decades ago. The difference lies in whether that legacy is maintained, reviewed, and adapted to current threats and uses.
That is where Microsoft faces the harder challenge. Windows 11 wants to be more modern, lighter, more secure, and better prepared for local AI. At the same time, it must continue running Win32 applications that many companies consider essential. This tension explains some of the criticism aimed at the system: the feeling of old and new interfaces being mixed together, duplicated settings panels, background processes, inherited services, and an experience that sometimes seems to move forward by piling up layers.
Russinovich is not just any voice in this debate. Besides his role at Azure, he is a highly respected figure among system administrators, developers, and Windows experts because of Sysinternals, the advanced toolset he created in 1996 to diagnose, manage, and better understand Windows. Microsoft now maintains Sysinternals as an essential collection for IT professionals and developers, with utilities such as Autoruns, ProcDump, Sysmon, Process Explorer, and ZoomIt.
That background makes his comment more interesting. It sounds less like an apology and more like a technical reminder: Windows cannot reinvent itself from scratch without breaking a huge part of its own value. The difficult part is modernizing without destroying compatibility.
AI does not remove legacy; it makes it more important
The debate comes just as Microsoft is trying to position Windows as a platform prepared for artificial intelligence. The company has talked about PCs with NPUs, Copilot, automation, agents, and experiences more deeply integrated into the operating system. But any future version of Windows will have to coexist with the Win32 base for a long time.
That is not necessarily a bad thing. Many professional applications that could benefit from local AI are precisely traditional desktop applications: editing, engineering, CAD, business management, development, cybersecurity, monitoring, system administration, data analysis, or internal tools. If Microsoft wants AI to reach all that software, it needs a way to connect modern capabilities with existing applications, not ask everyone to rewrite everything from scratch.
Windows App SDK represents part of that strategy: giving access to modern features without forcing developers to immediately abandon familiar frameworks. The challenge will be doing this coherently, with good performance and without adding even more complexity. Developers have spent years hearing new names in the Windows ecosystem, from UWP to WinUI, Project Reunion, and Windows App SDK. Clarity matters.
Performance matters too. In recent years, many users have criticized Windows for feeling heavier than necessary, especially compared with more tightly controlled systems such as macOS or lightweight Linux distributions. Dependence on Win32 is not the only cause, but it is part of an architecture where native applications, web components, cloud services, telemetry, enterprise compatibility, and new AI functions coexist.
Legacy can be an advantage if it does not become a burden
The big question is not whether Windows should erase Win32. It cannot do that without breaking its ecosystem. The question is whether Microsoft can turn that legacy into an advantage rather than an excuse. Maintaining compatibility should not prevent improvements in performance, security, visual consistency, memory use, or reliability.
In fact, Win32 remains highly relevant because many native applications offer something users increasingly value: speed, low resource use, and control. After years of web apps packaged as desktop software, many developers and users are once again appreciating well-built native software. In that sense, the old API is not just a relic. It is also a way to create efficient applications when used properly.
The problem appears when legacy builds up without order. When there are duplicated settings, overlapping APIs, hidden old control panels, components that are hard to audit, or dependencies nobody dares to touch. At that point, compatibility stops being a virtue and becomes technical debt.
Windows 11 will keep relying on Win32 because the real world still needs that bridge to decades of software. The news is not that old code exists, but that Microsoft recognizes it as a living part of its strategy. If it maintains it well, Win32 can remain a solid foundation. If it drags it along without modernization, it will become an increasingly visible burden.
The future of Windows will probably not be a clean break between old and new. It will be a long coexistence between Win32, Windows App SDK, modern applications, local AI, cloud services, and enterprise tools. In operating systems, progress does not always mean erasing the past. Sometimes it means making sure the past does not prevent the future from moving forward.
Frequently asked questions
Does Windows 11 still use Win32?
Yes. Win32 remains a central part of the Windows ecosystem, and Microsoft continues to maintain active documentation for building desktop applications with this API.
Does that mean Windows 11 is old or insecure?
Not necessarily. A technology being decades old does not make it insecure by itself. What matters is how it is maintained, audited, and integrated with the modern layers of the system.
What is Windows App SDK?
Windows App SDK is Microsoft’s modern set of APIs and tools for building Windows applications, compatible with technologies such as WinUI 3, WPF, Windows Forms, and Win32.
Why doesn’t Microsoft remove Win32?
Because it would break compatibility with a huge number of enterprise, professional, and industrial applications that still depend on that foundation.