What "Could Not Read Username: No Such Device or Address" Actually Means
This error appears when your computer or phone cannot find the account information it is trying to load. The message breaks down into two parts: your device cannot read the username (the first problem), and it cannot locate the device or address where that username lives (the second problem). This usually happens during login, when you restart your computer, or when you try to access a shared folder or network resource.
The error is not saying your username is wrong. It is saying your device cannot reach the place where usernames are stored — either because that storage location has moved, disappeared, or your device lost its connection to it. Think of it like trying to call a phone number that is no longer in service: the number itself might be correct, but the line does not exist anymore.
Key Takeaways
- This error usually means your device lost contact with the server or storage location that holds your username information, not that your username itself is incorrect.
- On a home computer, restart your device first — this fixes the problem in most cases by reloading the connection to your local user account.
- On a work or school network, contact your IT department or help desk, because they control the server your device is trying to reach.
- If you are trying to access a shared folder or external drive, check that the device or network location is powered on and connected before trying again.
- Changing your network settings, removing a device from the network, or updating Windows or macOS can trigger this error until your device reconnects properly.
Why This Happens on Your Home Computer
On a personal computer, your username and password are stored locally — on your own hard drive, not on a distant server. When Windows or macOS cannot read that local storage, you see this error. The most common cause is a temporary glitch during startup, where your device has not finished loading all its own files yet.
Restarting your computer fixes this in most cases. When you restart, your device reloads the entire file system from scratch, including the part that stores your username. If the error persists after a restart, your hard drive may have a problem reading files, or a recent update may have corrupted the account information. In either case, you will need to troubleshoot further or contact a technician who can examine your hard drive.
When This Error Appears on a Work or School Network
If you see this error on a computer that is part of a workplace or school network, your device is trying to read your username from a network server instead of from your local hard drive. The server might be offline, your device might have lost its network connection, or the server might no longer recognize your device.
Contact your IT department or help desk when ready — they can check whether the server is running, whether your device is still registered on the network, and whether your account still exists. Do not try to fix this yourself, because network authentication involves security settings that only your IT team should change. Tell them the exact error message and when it started appearing.
Accessing Shared Folders or External Drives
This error also appears when you try to open a shared folder on another computer, a network drive, or an external hard drive. Your device is looking for the username that has permission to access that shared resource, but it cannot find the device or server where that username is stored.
First, check that the device holding the shared folder is powered on and connected to the same network. If you are trying to access a shared folder on another computer in your home, make sure that computer is awake (not in sleep mode) and that file sharing is turned on in its settings. If you are trying to access a network drive at work, check with your IT department to confirm the drive is online. If the device is on and connected, try disconnecting and reconnecting to the shared resource, or restart your own device.
After a Windows or macOS Update
Major operating system updates sometimes change how your device stores or reads username information. After you update Windows or macOS, your device may temporarily lose contact with your local user account or with a network server. This is usually temporary — your device needs time to finish installing the update and reconnecting to the places where usernames are stored.
Wait at least 15 minutes after an update completes, then restart your device. If the error still appears, check the manufacturer's website (Microsoft for Windows, Apple for macOS) to see whether other users have reported the same problem after this update. If they have, a follow-up patch may already be available. If not, contact support with the exact update version and the error message.
Removing a Device from Your Network
If you recently removed a computer or external drive from your network, or if you deleted a network location from your device's settings, your device may still be trying to read usernames from that missing location. You will see this error when your device looks for that resource and cannot find it.
Open your device's network settings and remove any network locations or devices that no longer exist. On Windows, go to Settings > Network > Advanced Network Settings and look for "Network Drives" or "Mapped Drives" — delete any that point to devices you no longer use. On macOS, open Finder, go to Preferences, and remove any network locations from the Favorites list. After you clean up these old connections, restart your device.
When to Contact a Technician
If restarting your device does not fix the error, and you are not on a work or school network, your hard drive may have a problem reading files. This is beyond what most people can fix on their own. A technician can run diagnostic tools to check your hard drive's health and repair corrupted account information if it is still recoverable.
Before you contact a technician, write down exactly when the error started, what you were doing when it appeared, and whether you made any changes to your device recently (new software, a network change, an update). This information helps a technician narrow down the cause quickly.
Frequently Asked Questions
Can I log in with a different username to fix this?
If you have another user account on the same computer, try logging in with that account. If it works, the problem is specific to your main account. If the other account also shows the error, the problem is with your device itself, not your username. Either way, you now know whether to troubleshoot your account or your device's file system.
Does this mean my password is compromised?
No. This error means your device cannot find where your username is stored, not that someone has accessed your account. Your password is not involved in this particular error. If you are worried about account security for other reasons, change your password on a different device, but this error alone does not indicate a breach.
What if I see this error only when I try to access one specific shared folder?
The problem is with that particular shared resource, not with your device or username. Check that the computer or server holding the folder is powered on and connected. Ask the person who manages that shared folder whether they recently moved it, changed its permissions, or took it offline. They may need to re-share it or update your access.
Will restarting my computer delete my files?
No. Restarting your computer shuts it down and turns it back on — it does not delete anything. Your files stay on your hard drive. Restarting is safe and is the first step to try for almost any error message.
Is this error related to my internet connection?
Only if you are trying to access a network resource or a cloud service. If the error appears when you try to log into your own computer, your internet connection is not the problem — your device is trying to read information from your local hard drive, which does not need the internet. If the error appears when you try to access a shared folder or network drive, then yes, your network connection matters, and you should check that you are connected.