The main reason a user profile, in most instances a domain profile, appears in User Profile Manager with the headline Account Unknown is that its SID (security ID) is invalid, or it’s just a hidden security account.

The SID (security identification) Account Unknown signifies that the User Profile is no longer active. You can notice this when an account isn’t properly deactivated or the account is actually a disguised security account.

Read this article till the end to know the details about this account and what you should do with it.

How and Why Does ‘Account Unknown s-1-15-3’ Appear?

As you may already know, in Windows, when you right-click on the Local Disk (C), select Properties, and go to the Security tab on the property sheet, you should be able to find the Account Unknown SIDs along with other permission entries under Groups or user names. If you click on the Advanced option, you can learn more about the SIDs mentioned there. This should bring you to the window for Advanced Security Settings. 

To tell the truth, this isn’t actually an error. This unknown account represents any of a few yet particular factors. Sometimes your system creates hidden security accounts with this Account Unknown tag that runs in the background. In general, they are meant to execute some administrative tasks such as installing updates, Windows security, file management, etc. If it’s the same as your case, you shouldn’t try to delete these accounts to ensure proper security.

Sometimes it indicates the SID of the account that no more exists on your system. When it has permissions, in the Security tab, you can see only the account’s SID instead of its actual name. For easier understanding, when you check for permissions, all accounts are displayed by their name. But when any of them get deleted, it actually doesn’t get removed from the places where it has permissions. There, it stays shown by its full SID as the system doesn’t provide a name for this account.

Additionally, they can be the Capability SIDs. They are generally used for providing permissions for various applications. For instance, one of the s-1-15-3 SIDs is associated with NVIDIA. 

What Should You Do With The How ‘Account Unknown s-1-15-3’?

It doesn’t matter if the unknown accounts are either security accounts or invalid accounts, you mustn’t try to remove them. We assure you that these accounts are genuinely harmless and you don’t have to worry about them. If you forcefully try removing them, as a result, you’ll cause any of the following incidents –

• Reduce Windows security.
• Face problems while accessing files.
• Bring instability to your system, even can break it.

Therefore, it’s recommended to not attempt to delete those Account Unknown SIDs. It’ll be wise if you just let them stay as they are and don’t try to access them.

Frequently Asked Questions (FAQs)

How do I delete an unknown account on Windows 10?

The procedure is pretty simple. Just navigate through Control Panel > All Control Panel Items > User Accounts > Manage Accounts. After that, select the unknown account or user you want to delete. Finally, simply delete it.  

How do I remove an unknown account on Windows 11?

In this case, you’ve to remove it in another way. First of all, press Win + R to bring the Run window. Here, type netplwiz and go for it. Check for the accounts that are not relevant or familiar to you. Lastly, click on the accounts one by one and remove them.

What causes a corrupted user account?

There are some significant issues that can cause a corrupted user account. Such as – unexpected power outages while processing an important system task, file system integrity being compromised due to disk write issues, strong malware attacks, the user account missing according to your system, etc. 

Conclusion

So far, we’ve provided all the prominent information about this Account Unknown s-1-15-3 including its origin. In short, it is not any bug or mysterious virus which will damage your PC. So, rest assured!! Your PC is not at risk. If you find this post useful, share your valuable feedback with us.