Normally, Windows prompts you to download .NET Framework 3.5 via Windows Update when an application requests it. However, an offline installer or offline enablement method is highly necessary in several scenarios:
Perfect for isolated workstations, secure enterprise environments, or PCs with slow/metered internet connections.
Open This PC and note the drive letter assigned to the mounted media (for example: Drive D: , E: , or F: ).
Double-click your Windows 10 or Windows 11 ISO file to mount it as a virtual drive. Alternatively, insert your Windows installation USB or DVD. Normally, Windows prompts you to download
Insert your Windows 10 or 11 USB drive, or double-click your Windows ISO file to mount it. Note the drive letter (e.g., D: or E: ).
Downloading executable files from unofficial repositories exposes your machine to severe malware, spyware, and unauthorized system modifications. Because Microsoft provides the source files completely free of charge directly inside your official Windows OS ISO media, you never have to put your security at risk using unverified third-party tools.
Method 1: The Official Native Method (Using Windows 10/11 Installation Media) Double-click your Windows 10 or Windows 11 ISO
The .NET Framework 3.5 is essential for running many older desktop applications on modern operating systems. While Windows 10 and Windows 11 ship with newer versions like .NET 4.8 pre-installed, they do not enable version 3.5 by default. Attempting to install it online can sometimes fail due to network restrictions, Windows Update errors, or lack of internet access.
Tools like the "DotNetFx35 Offline Installer" operate as portable freeware. They present a small application window where you click "Browse" to select your Windows ISO sources\sxs directory, and then click "Install."
Look at the very top of the list for .
Microsoft .NET Framework 3.5 Service Pack 1 (Full Package) .
By following these steps, you should be able to download and install the .NET Framework 3.5 offline installer for Windows 10/11.
If you need help checking your to find a matching ISO file, or if you are running into a specific installation error code not listed above, please let me know so I can provide customized troubleshooting steps! Share public link Note the drive letter (e