.net framework for windows 11 26H2 version

For Windows 11 labeled 26H2, check the OS build first: use the standalone .NET Framework 3.5 installer only on build 28000 or later; on build 26300.x, enable the built-in NetFx3 Windows feature instead.

1. Check the Windows build

Press Windows+R, enter:

winver

Then use the applicable option below.

If the build is 28000 or later

Download the official .NET Framework 3.5 standalone installer:

Download .NET Framework 3.5 for Windows 11 26H1 and later

Microsoft specifies that this package applies to Windows 11 26H1 build 28000 and later, and that it works only with the Windows version specified ^1^.

For an unattended installation, the standalone installer supports /q and /quiet ^2^.

If the build is 26300.x

Do not use the build-28000 standalone package. No separate Microsoft standalone .NET Framework 3.5 package for build 26300.x is identified in the available guidance, and the build-28000 installer rejects that build.

Instead:

1. Press Windows+R.
2. Enter optionalfeatures.exe.
3. Select .NET Framework 3.5 (includes .NET 2.0 and 3.0).
4. Select OK and allow Windows Update to obtain the required files.
5. Restart if prompted.

This method was confirmed for the matching Windows 11 26H2/build-26300 scenario ^3^.

If Windows Update cannot provide the files, mount installation media matching the same Windows build, edition, architecture, and language, then run this from an elevated Command Prompt, replacing D: with the mounted ISO drive:

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All ^
 /Source:D:\sources\sxs /LimitAccess

Microsoft documents Windows installation media as the supported offline source for Windows versions where .NET Framework 3.5 remains a Windows component ^4^.

If you need .NET Framework 4.x instead

Windows 11 releases from 22H2 onward include .NET Framework 4.8.1. Framework 4.x releases are in-place updates, so an older 4.x version cannot be installed alongside or over a later version ^5^.

Therefore:

• Application requires .NET Framework 2.0, 3.0, or 3.5 → install/enable 3.5 using the build-specific method above.
• Application requires .NET Framework 4.x → use the included 4.8.1; do not install an older 4.x standalone package.
• Application requires modern .NET 8, 9, or 10 → that is a separate product from .NET Framework and requires its corresponding runtime ^6^.

References

1. Install .NET Framework 3.5 on Windows 11
2. .NET Framework 3.5 on Windows 11 FAQ
3. .NET Framework 3.5 standalone installer for Windows 11 26H1+ requires build 28000, but Windows 11 26H2 uses build 26300 - Microsoft Q&A
4. Install .NET Framework 3.5 on Windows 10 and Windows Server
5. Install .NET Framework on Windows and Windows Server
6. Install .NET on Windows