0x800f081f
Moderate
Microsoft · Windows
Source files for .NET Framework 3.5 or other optional Windows features could not be found. The Component Based Servicing (CBS) system cannot locate the required installation source.
Quick Answer
Error code 0x800F081F on your Microsoft Windows means: Source files for .NET Framework 3.5 or other optional Windows features could not be found. The Component Based Servicing (CBS) system cannot locate the required installation source.. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Enable .NET Framework 3.5 via DISM with Windows Update as source: Open Command Prompt as Administrator and run: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /Source:https://download.microsoft.com /LimitAccess.
2
If you have Windows installation media (USB or ISO), mount it and run: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /Source:D:\sources\sxs (replace D: with your media drive letter).
3
Check Group Policy settings: Open gpedit.msc, navigate to Computer Configuration > Administrative Templates > System. Open 'Specify settings for optional component installation and component repair' and either disable it or enable it with 'Contact Windows Update directly to download repair content instead of WSUS' checked.
4
Repair the component store: Run DISM /Online /Cleanup-Image /RestoreHealth, then try enabling the feature again.
5
If on a domain with WSUS, ask your IT administrator to ensure .NET Framework 3.5 source files are available on the WSUS server, or temporarily configure the machine to use Microsoft Update directly.
6
Download the .NET Framework 3.5 offline installer from the Microsoft Download Center and install it directly.
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
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