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Fix Windows Defender Update fails with error 0x80070643

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If you are trying to update Windows Defender using Windows Update, then you may have to face error code 0x80070643 which accompanies the error message “Definition Update for Windows Defender – Error 0x80070643”. The error code typically means that a fatal error has occurred during the installation, but there is no particular cause associated with this error. Also, the error doesn’t really provide much information, but Microsoft has acknowledged the issue, and this is their official statement:

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Thank you for your patience regarding Windows Defender update error 0x80070643. We are aware of the issue and trying to roll out mitigation as soon as possible. Meanwhile, to get your machine back to a protected state, you can manually download and apply the latest Definition Update.

Fix Windows Defender Update fails with error 0x80070643

Now there are few fixes or workaround the problem, but you need to try them all because what may work for one user doesn’t necessarily mean that it will work for another user. So without wasting any time let’s see how to Fix  Windows Defender Update fails with error 0x80070643 with the help of below-listed troubleshooting guide.

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Fix Windows Defender Update fails with error 0x80070643

Make sure to create a restore point just in case something goes wrong.

Method 1: Update Windows Defender Manually

1. Press Windows Key + Q to bring up Windows Search, type Windows Defender and click on the search result.

Type Windows Defender and click on the search result | Fix Windows Defender Update fails with error 0x80070643

2. Navigate to Update > Update definitions.

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3. Click on Update and wait for Windows Defender to download and install updates.

Click on Update and wait for Windows Defender to download and install updates

4. Reboot your PC to save changes.

Method 2: Temporarily Disable 3rd party Antivirus

1. Right-click on the Antivirus Program icon from the system tray and select Disable.

Disable auto-protect to disable your Antivirus

2. Next, select the time frame for which the Antivirus will remain disabled.

select the duration until when the antivirus will be disabled

Note: Choose the smallest amount of time possible, for example, 15 minutes or 30 minutes.

3. Once is done, again try to run Windows Defender and see if you’re able to Fix Windows Defender Update fails with error 0x80070643.

Method 3: Run SFC and CHKDSK

1. Open Command Prompt. The user can perform this step by searching for ‘cmd’ and then press Enter.

Open Command Prompt. The user can perform this step by searching for ‘cmd’ and then press Enter.

2. Now type the following in the cmd and hit enter:

Sfc /scannow
sfc /scannow /offbootdir=c:\ /offwindir=c:\windows

SFC scan now command prompt

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3. Wait for the above process to finish and once done, restart your PC.

4. Next, run CHKDSK to Fix File System Errors.

5. Let the above process complete and again reboot your PC to save changes.

Method 4: Perform Clean Boot

Sometimes 3rd party software can conflict with Windows and can cause the issue. To Fix Windows Defender Update fails with error 0x80070643 Issue, you need to perform a clean boot on your PC and diagnose the issue step by step.

Under the General tab, enable Selective startup by clicking on the radio button next to it

Method 5: Use the command prompt to update Windows Defender

1. Open Command Prompt. The user can perform this step by searching for ‘cmd’ and then press Enter.

2. Type the following command into cmd and hit Enter after each one:

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“%PROGRAMFILES%\Windows Defender\MPCMDRUN.exe” -RemoveDefinitions -All

“%PROGRAMFILES%\Windows Defender\MPCMDRUN.exe” -SignatureUpdate

Use the command prompt to update Windows Defender | Fix Windows Defender Update fails with error 0x80070643

3. Once the command finishes processing, close cmd and reboot your PC.

Method 6: Reset Windows Updates Components

1. Open Command Prompt. The user can perform this step by searching for ‘cmd’ and then press Enter.

2. Now type the following commands to stop Windows Update Services and then hit Enter after each one:

net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver

Stop Windows update services wuauserv cryptSvc bits msiserver

3. Next, type the following command to rename SoftwareDistribution Folder and then hit Enter:

ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old

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Rename SoftwareDistribution Folder

4. Finally, type the following command to start Windows Update Services and hit Enter after each one:

net start wuauserv
net start cryptSvc
net start bits
net start msiserver

Start Windows update services wuauserv cryptSvc bits msiserver

5. Reboot your PC to save changes and check if you can Fix Windows Defender Update fails with error 0x80070643.

Method 7: Run Windows Update Troubleshooter

1. Open control panel and then search Troubleshooting in the Search Bar on the top right side and click on Troubleshooting.

Search Troubleshoot and click on Troubleshooting

2. Next, from the left window, pane select View all.

3. Then from the Troubleshoot computer problems list select Windows Update.

From the Troubleshoot computer problems list select Windows Update

4. Follow on-screen instruction and let the Windows Update Troubleshoot run.

Windows Update Troubleshooter | Fix Windows Defender Update fails with error 0x80070643

5. Restart your PC, and you may be able to Fix Windows Defender Update fails with error 0x80070643.

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That’s it you have successfully Fix Windows Defender Update fails with error 0x80070643 but if you still have any questions regarding this post then feel free to ask them in the comment’s section.

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