A Windows security update failed: identify it before retrying

Windows Update can fail because of storage, a pending restart, a component problem or another cause. Repeating an unknown installer or deleting update files at random can make diagnosis harder. The useful starting point is the failed update's exact identity, date and error code.

Before you start​

Save current work and check that a recoverable backup exists for important files. Note whether the device is managed by an employer; their update policy may control the retry.

Do it step by step​

1. Open Settings, Windows Update, then Update history. Locate the failed entry and record its KB number or feature name plus the error code.
2. Check for a pending restart and available disk space. Complete a requested restart before attempting another update.
3. Use Microsoft's official guidance for that error or the Windows Update troubleshooter where offered; avoid third-party 'update repair' downloads.
4. Retry through Windows Update once after addressing the identified cause. Do not install an unrelated package simply because its KB number looks nearby.
5. Return to Update history and confirm the exact update now shows installed. If failure persists, record the new error and use Microsoft or your organization's support channel.

Check the result​

The same update should appear as successfully installed, and Windows Update should no longer request it. A restart may be required before the result is final.

If something goes wrong​

If an update is not listed or fails with a different code, stop treating it as the same problem. Use the current error and system version in official support material.

Know the limit​

Update history is evidence of installation state, not a complete vulnerability scan. Microsoft advises looking up the failed update's code before applying a fix. Microsoft's update error guidance Microsoft's Windows Update FAQ