How to Fix Windows Update Error 0x80070643 [8 Solutions]

Quick Fix

Run the Windows Update Troubleshooter first. Press Windows + I, go to System > Troubleshoot > Other troubleshooters, and run “Windows Update.” This automatically fixes the most common causes of error 0x80070643.

You’re trying to update Windows, and instead of a smooth installation, you get slapped with error code 0x80070643. The update fails, you retry, it fails again. Classic Windows behavior.

This error usually means something went wrong with the .NET Framework or Windows Defender definitions during the update. The good news? It’s almost always fixable without reinstalling Windows or calling tech support.

What Causes Error 0x80070643?

This error code pops up for several reasons:

• Corrupted .NET Framework – The most common cause, especially after interrupted updates
• Windows Defender definition conflicts – Security updates sometimes clash with existing definitions
• Damaged Windows Update components – Cache files got corrupted somewhere along the way
• Third-party antivirus interference – Your antivirus might be blocking update files
• Insufficient disk space – Updates need temporary space to install
• Corrupted system files – Windows components got damaged

The error code itself isn’t very descriptive, which is why troubleshooting requires trying a few different approaches.

How to Fix Windows Update Error 0x80070643

1. Run the Windows Update Troubleshooter

Start with the built-in troubleshooter. It’s surprisingly effective and takes about 2 minutes.

1. Press Windows + I to open Settings
2. Go to System > Troubleshoot
3. Click Other troubleshooters
4. Find Windows Update and click Run
5. Wait for it to detect and fix problems
6. Restart your computer when prompted
7. Try the update again

If the troubleshooter finds issues but can’t fix them automatically, it’ll tell you what’s wrong – which helps narrow down the solution.

2. Manually Update Windows Defender

If the failing update is a Windows Defender definition update, manually updating it often bypasses the error.

1. Open Windows Security (search for it in the Start menu)
2. Click Virus & threat protection
3. Under “Virus & threat protection updates,” click Check for updates
4. Click Check for updates again on the next screen
5. Let it download and install the latest definitions

Alternatively, download definitions directly from Microsoft:

1. Go to Microsoft Security Intelligence
2. Download the appropriate version for your system (64-bit or 32-bit)
3. Run the downloaded file to install manually

3. Repair the .NET Framework

A corrupted .NET Framework causes this error frequently. Microsoft has a repair tool specifically for this.

1. Download the .NET Framework Repair Tool from Microsoft’s website
2. Run the downloaded file
3. Accept the license agreement
4. Let it scan for issues (takes 5-10 minutes)
5. Apply the recommended fixes
6. Restart your computer
7. Try Windows Update again

If the repair tool doesn’t help, you might need to reinstall .NET Framework completely – but try the other fixes first.

4. Reset Windows Update Components

This clears out corrupted cache files and resets the update service. You’ll need to run Command Prompt as Administrator.

1. Press Windows key, type cmd
2. Right-click Command Prompt and select Run as administrator
3. Run these commands one at a time, pressing Enter after each:

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

4. Close Command Prompt
5. Restart your computer
6. Run Windows Update

This essentially gives Windows Update a fresh start by clearing its download cache and resetting its database.

5. Run System File Checker (SFC)

Corrupted Windows system files can prevent updates from installing. SFC scans and repairs these files.

1. Open Command Prompt as Administrator (same as step 4)
2. Type this command and press Enter:

sfc /scannow

3. Wait for the scan to complete (usually 10-15 minutes)
4. If it finds and fixes issues, restart and try updating
5. If it says it found issues but couldn’t fix them, run DISM next

6. Run DISM to Repair Windows Image

DISM goes deeper than SFC and can fix problems that SFC can’t handle.

1. Open Command Prompt as Administrator
2. Run this command:

DISM /Online /Cleanup-Image /RestoreHealth

3. This takes 15-30 minutes – don’t interrupt it
4. When it finishes, run sfc /scannow again
5. Restart your computer
6. Try Windows Update

DISM downloads fresh copies of damaged files from Windows Update, so you need an internet connection.

7. Temporarily Disable Third-Party Antivirus

Some antivirus programs interfere with Windows Update by blocking or quarantining update files.

1. Find your antivirus icon in the system tray (bottom-right corner)
2. Right-click it and look for “Disable,” “Pause protection,” or similar
3. Disable it temporarily (choose 15 minutes or until restart)
4. Run Windows Update immediately
5. Re-enable your antivirus after the update completes

If this works, check your antivirus settings for a “gaming mode” or “silent mode” that’s less aggressive during updates.

8. Install the Update Manually

If automatic updates keep failing, you can download and install the specific update manually.

1. Note the KB number of the failing update (e.g., KB5034441)
2. Go to Microsoft Update Catalog
3. Search for the KB number
4. Download the version matching your Windows (x64 for 64-bit, x86 for 32-bit)
5. Run the downloaded file to install manually
6. Restart when prompted

Manual installation bypasses some of the automatic update mechanisms that might be causing problems.

9. Check Your Disk Space

Windows updates need free space to download and install. If you’re low on space, updates will fail.

1. Open File Explorer
2. Check your C: drive – you need at least 10-20 GB free for major updates
3. If you’re low on space:
   • Run Disk Cleanup (search for it in Start menu)
   • Delete files from Downloads folder
   • Empty the Recycle Bin
   • Uninstall programs you don’t use
4. Try the update again

If Nothing Works

Still stuck? Here are some last-resort options:

• Perform an in-place upgrade – Download Windows 11/10 ISO from Microsoft and run setup.exe. Choose “Keep files and apps” to reinstall Windows while preserving your data
• Hide the problematic update – Use Microsoft’s “Show or Hide Updates” tool to skip the failing update until a fixed version is released
• Wait it out – Sometimes Microsoft releases buggy updates. Check Reddit or tech forums to see if others are having the same problem

Preventing Future Update Errors

• Keep at least 20 GB free on your system drive
• Don’t interrupt updates – Let them finish, even if they take a while
• Update regularly – Letting updates pile up increases the chance of conflicts
• Restart when prompted – Postponing restarts can cause update issues

FAQ

Is error 0x80070643 serious?

Not usually. It’s an installation failure, not a sign of hardware problems or malware. Your computer will keep working fine – you just can’t install that particular update until you fix the underlying issue.

Can I ignore this error?

For regular updates, you can temporarily skip it. But security updates (especially Windows Defender definitions) should be installed to keep your system protected. Try the manual update method if automatic updates keep failing.

Why does this error keep coming back?

If you’ve fixed it once but it returns, you likely have an underlying issue with Windows Update components or corrupted system files. Run through the SFC and DISM steps again, or consider an in-place Windows reinstall.

Does this error mean my Windows is corrupted?

Not necessarily. It usually means specific update components or .NET Framework files are damaged – not your entire Windows installation. The repair steps above fix these specific issues without affecting the rest of your system.

Wrapping Up

Error 0x80070643 is annoying but fixable. Start with the Windows Update Troubleshooter and manually updating Windows Defender – these solve the problem for most people. If that doesn’t work, resetting Windows Update components and running SFC/DISM usually does the trick.

The key is to work through the fixes systematically rather than jumping straight to drastic measures like reinstalling Windows. Most of the time, you’ll have it sorted in under 30 minutes.