Windows Update 0x80070643 Keeps Failing — Fix 2026
Your Windows update keeps failing at the same percentage and the error code 0x80070643 is giving you zero useful information. You've already tried restarting, but the update refuses to install.
Why this happens: This error killed half a day for me before I found the one fix that actually works: the catalog bypass.
What you need: You need an active internet connection and your specific KB number from the Windows Update history screen.
Fix Steps
1. Open the Start menu, search for
Windows Update, and open the settings page to find the specific KB number that failed.2. Go to the [Microsoft Update Catalog](https://catalog.update.microsoft.com) in your web browser.
3. Search for your KB number and select the download button that matches your system architecture, typically
Windows 10 x64 or Windows 11 x64.4. Click the link provided in the pop-up window to download the
.msu file.5. Double-click the downloaded file and click
Yes when the installer prompt appears.6. Wait 1 to 3 minutes for the installation to finish and then restart your computer.
7. Return to
Windows Update settings and click Check for updates to verify the KB number is gone.If that didn't work: If the KB number still appears, it may require a different manual step specific to that update; check your exact KB number again or try running the Windows Update Troubleshooter.
Did this fix your issue? Subscribe for more quick IT solutions.
Subscribe to kitsunefix