How To Install .NET Framework 3.5 Offline in Windows 10 (2026 Guide)

Quick Answer: To install .NET Framework 3.5 offline in Windows 10, mount your Windows 10 ISO or insert your Windows installation USB/DVD, then open Command Prompt as Administrator and run:

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

Replace X: with the drive letter of your Windows installation media. Windows will install .NET Framework 3.5 without downloading files from Windows Update.

Although Windows 10 is no longer Microsoft’s newest operating system, millions of PCs still use it every day. Many older applications, business software, legacy utilities, and classic PC games still depend on .NET Framework 3.5, which isn’t always enabled by default.

If your PC doesn’t have an internet connection or Windows Update fails to download the required files, you can install .NET Framework 3.5 offline using your Windows 10 installation media.

Follow the steps below.

Table of Contents

Install .NET Framework 3.5 Offline Using DISM

Step 1: Mount the Windows 10 ISO

Locate your Windows 10 ISO file and double-click it to mount it. If you’re using a Windows installation USB or DVD, simply insert it into your computer.

Step 2: Open Command Prompt as Administrator

Search for Command Prompt, right-click it, and select Run as administrator.

Step 3: Run the DISM Command

Enter the following command and press Enter:

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

Replace D: with the drive letter assigned to your mounted ISO, USB drive, or DVD.

For example, if your installation media appears as E:, use:

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

Windows will begin installing .NET Framework 3.5 from the installation media. Once the process reaches 100%, restart your computer if prompted.

Automatic Offline Installation Using a Batch File

If you’d rather not type commands manually, you can automate the installation process.

Open Notepad.
Copy and paste the script below.
Save the file with a .bat extension (for example, Install-NetFx3.bat).
Mount your Windows 10 ISO or connect your installation USB/DVD.
Right-click the batch file and choose Run as administrator.

@echo off
Title .NET Framework 3.5 Offline Installer

for %%I in (D E F G H I J K L M N O P Q R S T U V W X Y Z) do (
    if exist "%%I:\sources\sxs" set setupdrv=%%I
)

if defined setupdrv (
    echo Found installation media on drive %setupdrv%
    echo.
    echo Installing .NET Framework 3.5...
    DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /Source:%setupdrv%:\sources\sxs /LimitAccess
    echo.
    echo Installation complete.
) else (
    echo No Windows installation media was found.
    echo Please mount the Windows ISO or connect your Windows installation USB/DVD and try again.
)

pause

The script automatically detects the Windows installation media and installs .NET Framework 3.5 without requiring you to edit the drive letter.

Troubleshooting

Error 0x800F081F

This usually means Windows cannot find the required installation files. Make sure you’re using installation media that matches your installed version of Windows 10.

Error 0x800F0954

This error commonly occurs on computers managed by an organization using WSUS. Installing from local installation media with the DISM command above usually resolves the issue.

“The source files could not be found”

Verify that the sources\sxs folder exists on your Windows installation media and that you’ve entered the correct drive letter.

Frequently Asked Questions

Do I still need .NET Framework 3.5 in 2026?

Yes. Many older desktop applications, enterprise software, accounting programs, and classic PC games still require .NET Framework 3.5 to run correctly.

Does this work without an internet connection?

Yes. As long as you have a Windows 10 installation ISO, USB drive, or DVD containing the sources\sxs folder, you can install .NET Framework 3.5 completely offline.

Will this affect newer .NET versions?

No. .NET Framework 3.5 installs alongside newer versions such as .NET Framework 4.8 and does not replace them.

If you’re facing installation errors or have questions about Windows 10, let us know in the comments and we’ll help you troubleshoot the issue.