unfortunately, a lot of the information on here will be outdated. the most up to date and accurate information can be found at the wiki and the guide.
the information here will continue to be served for a) backup/redundancy and b) archival.

Microsoftwindowsnetfx3ondemandpackagecab Download — Free Link

From the ISO, the file is at:
D:\sources\sxs\microsoft-windows-netfx3-ondemand-package.cab

You can copy it from there to your desktop. But again – it’s tied to that specific Windows build.

Warning: .cab installers for .NET Framework should come from Microsoft only. Do not use unknown third‑party downloads — they can contain malware. Steps below assume Windows 8, 8.1, 10, or 11 where .NET 3.5 is an optional feature or distributed via Microsoft update packages. microsoftwindowsnetfx3ondemandpackagecab download free link

Important: Microsoft does not provide a standalone direct .cab download link for public use from a simple browser URL. The recommended way to obtain the official .cab file is through the Microsoft Volume Licensing Service Center (VLSC) or Visual Studio Subscriptions for IT professionals.

However, for most users, the safest method is to let Windows download it on demand. If you specifically need the .cab file for offline deployment (e.g., via DISM), you can extract it from a mounted Windows installation ISO. Warning:

Best Practice – Use a Windows ISO (Official & Free):

Microsoft does not host this CAB file on a simple “click to download” public webpage for consumers. Instead, you can obtain it through three official channels. Important: Microsoft does not provide a standalone direct

Do not download from random file-sharing sites (e.g., mediafire, dropbox links from forums) — they may contain modified or malicious files.