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# 0x800f081f: How to Fix This Windows Update Error

> Fix Windows Update error 0x800f081f in Windows 10 and 11 with simple steps: DISM, SFC, resetting update components, and installing .NET Framework 3.5.

Error **0x800f081f** appears when Windows Update or DISM cannot find the files it needs to install an update or a Windows feature. It is most common when installing **.NET Framework 3.5** or a cumulative update on Windows 10 and Windows 11. This guide explains what causes the error and walks you through the fixes, from the quickest to the most thorough.

<Info>
  **Quick answer:** Run `DISM /Online /Cleanup-Image /RestoreHealth`, then `sfc /scannow`, restart your PC, and try Windows Update again. If the error appears while installing .NET Framework 3.5, use the installation media method in Fix 5.
</Info>

## What does error 0x800f081f mean?

The code 0x800f081f means **"The source files could not be found"** (`CBS_E_SOURCE_MISSING`). Windows tried to repair or add a component, but the required files were missing, damaged, or blocked.

You may see the message in one of these forms:

* `There were some problems installing updates... (0x800f081f)`
* `Error: 0x800f081f The source files could not be found.`
* `The changes couldn't be completed. Error code: 0x800F081F`

## Common causes

* Corrupted Windows system files or component store
* Damaged Windows Update cache
* .NET Framework 3.5 files not available on the PC
* A Group Policy setting that blocks Windows from downloading repair files
* An interrupted or partially downloaded update

## How to fix error 0x800f081f

Try the fixes in order. Restart your PC after each one and check Windows Update again.

### Fix 1: Run the Windows Update troubleshooter

<Steps>
  <Step title="Open troubleshooter settings">
    * **Windows 11:** Go to **Settings > System > Troubleshoot > Other troubleshooters**.
    * **Windows 10:** Go to **Settings > Update & Security > Troubleshoot > Additional troubleshooters**.
  </Step>

  <Step title="Run Windows Update troubleshooter">
    Select **Run** next to **Windows Update** and follow the on-screen instructions.
  </Step>

  <Step title="Restart and retry">
    Restart your PC and run Windows Update again.
  </Step>
</Steps>

### Fix 2: Repair system files with DISM and SFC

This is the most effective fix for 0x800f081f because it repairs the Windows component store.

<Steps>
  <Step title="Open Command Prompt as administrator">
    Search for **cmd**, right-click **Command Prompt**, and select **Run as administrator**.
  </Step>

  <Step title="Run DISM">
    ```bash theme={null}
    DISM /Online /Cleanup-Image /RestoreHealth
    ```

    Wait until it reaches 100%. This can take 10 to 20 minutes.
  </Step>

  <Step title="Run System File Checker">
    ```bash theme={null}
    sfc /scannow
    ```
  </Step>

  <Step title="Restart your PC">
    Restart and try installing the update again.
  </Step>
</Steps>

<Tip>
  If DISM itself fails with 0x800f081f, it cannot download repair files. Use Fix 5 to point DISM to a Windows ISO as the source.
</Tip>

### Fix 3: Reset Windows Update components

Clearing the update cache removes broken or incomplete downloads.

Open **Command Prompt as administrator** and run these commands one by one:

```bash Reset Windows Update theme={null}
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
```

Restart your PC and check for updates.

### Fix 4: Allow Windows to download repair content (Group Policy)

On Windows Pro, Enterprise, or Education, a policy may stop Windows from getting files from Windows Update.

<Steps>
  <Step title="Open Group Policy Editor">
    Press **Win + R**, type `gpedit.msc`, and press **Enter**.
  </Step>

  <Step title="Find the policy">
    Go to **Computer Configuration > Administrative Templates > System**.
  </Step>

  <Step title="Edit the setting">
    Open **Specify settings for optional component installation and component repair**, select **Enabled**, and check **Download repair content and optional features directly from Windows Update instead of Windows Server Update Services (WSUS)**.
  </Step>

  <Step title="Apply the change">
    Select **OK**, then run `gpupdate /force` in an administrator Command Prompt.
  </Step>
</Steps>

### Fix 5: Install .NET Framework 3.5 from Windows installation media

Use this fix if the error appears when turning on .NET Framework 3.5 or if DISM cannot find source files.

<Steps>
  <Step title="Get a matching Windows ISO">
    Download the Windows 10 or Windows 11 ISO from the official Microsoft website. The version must match your installed Windows.
  </Step>

  <Step title="Mount the ISO">
    Right-click the ISO file and select **Mount**. Note the drive letter (for example, `D:`).
  </Step>

  <Step title="Run DISM with the ISO as the source">
    Open Command Prompt as administrator and run (replace `D:` with your drive letter):

    ```bash theme={null}
    DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\sources\sxs
    ```
  </Step>

  <Step title="Restart your PC">
    Restart once the operation completes successfully.
  </Step>
</Steps>

### Fix 6: Install the update manually

<Steps>
  <Step title="Find the KB number">
    Go to **Settings > Windows Update > Update history** and note the KB number of the failed update (for example, KB5034441).
  </Step>

  <Step title="Download from Microsoft Update Catalog">
    Visit the [Microsoft Update Catalog](https://www.catalog.update.microsoft.com), search for the KB number, and download the version for your system (x64 or ARM64).
  </Step>

  <Step title="Install the update">
    Double-click the downloaded `.msu` file and follow the prompts.
  </Step>
</Steps>

### Fix 7: Repair upgrade with Windows installation media

If nothing else works, run an in-place repair upgrade. It reinstalls Windows system files and **keeps your apps and personal files**.

1. Mount the Windows ISO.
2. Run `setup.exe`.
3. Choose **Keep personal files and apps** when asked.

<Warning>
  Back up important files before a repair upgrade, just in case.
</Warning>

## How to prevent error 0x800f081f

* Keep enough free disk space (at least 20 GB) for updates.
* Do not shut down your PC while updates install.
* Run `DISM /Online /Cleanup-Image /RestoreHealth` occasionally to keep the component store healthy.
* Avoid third-party "cleaner" tools that delete Windows system files.

## Frequently asked questions

<AccordionGroup>
  <Accordion title="Is error 0x800f081f dangerous?">
    No. It does not harm your PC or data. It only means an update or feature could not install because source files were missing.
  </Accordion>

  <Accordion title="Does 0x800f081f happen on Windows 11?">
    Yes. The error occurs on both Windows 10 and Windows 11, and the same fixes work on both.
  </Accordion>

  <Accordion title="Why do I get 0x800f081f when installing .NET Framework 3.5?">
    Windows cannot find the .NET Framework 3.5 files locally or download them. Install it from a Windows ISO using DISM (Fix 5).
  </Accordion>

  <Accordion title="Which fix works best?">
    For most users, running DISM and SFC (Fix 2) followed by resetting Windows Update components (Fix 3) solves the problem.
  </Accordion>
</AccordionGroup>


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