Since "4.9" does not exist, here are the direct links to the latest official standalone installers:
While .NET Framework 4.8.1 is the latest for legacy Windows-only apps, Microsoft recommends using for any new projects to take advantage of cross-platform support and significantly better performance . net framework 49 offline installer for windows
Since ".NET 4.9" doesn't exist, here are the official alternatives you should actually use: Microsoft .NET Framework 4.8 offline installer for Windows Since "4
If you need to slipstream the update into a Windows image (WIM) or an offline servicing tool: While Microsoft has shifted focus towards the cross-platform
The .NET Framework is a software development platform developed by Microsoft that runs primarily on Microsoft Windows. It includes a large class library called Framework Class Library (FCL) and provides language interoperability across several programming languages. While Microsoft has shifted focus towards the cross-platform .NET (formerly .NET Core), the traditional .NET Framework remains essential for legacy enterprise applications and specific Windows desktop integrations.