USB device not recognized: how to fix it

You plug in a USB drive, printer, phone or other device and nothing happens, or Windows says USB device not recognized. Find out whether the cause is the port, the cable, the power, or the device, on Windows or Mac.

Before you start

Most of these fixes take a minute or two. You need the device, its cable if it has one, and a second computer if you have one, because testing there tells you which side is at fault. If the device holds files you need, do not format or erase it. None of the fixes in this guide erase data.

Windows may show different messages. "The last USB device you connected to this computer malfunctioned" and "Unknown USB Device" both point to the same group of causes: a loose or faulty cable or port, too little power, a driver problem, or a failing device.

Try these fixes in order

1. Reseat the device and try another port (2 minutes)

1. Unplug the device. Wait about a minute, then plug it back in firmly.
2. Plug it into a different USB port. Use a port on the computer itself, not on a keyboard, monitor or hub. On a desktop, the ports on the back of the case connect straight to the motherboard and often work more reliably than the front ones.
3. If it works in a different port, the first port may be loose or faulty. Plug another device into the first port to see if that fails too.

If the device works, you are done. Otherwise, go on.

2. Change the cable and remove the hub

1. Swap the cable for another that you know works. Some cables only charge and carry no data, so a phone or drive may charge but never appear on the computer.
2. Remove any hub or extension and connect the device directly. Microsoft notes that a non-powered hub may not give a drive enough power. Apple advises matching the speed of the device to the hub and plugging a self-powered hub into its power adapter.
3. Unplug other USB devices that you do not need, leaving only the one you are testing and the keyboard and mouse.

3. Restart and install updates (5 to 15 minutes)

1. Restart the computer with the device unplugged, then plug it in once the desktop appears.
2. On Windows, open Settings then Windows Update (Windows 10: Settings then Update & Security then Windows Update). Select Check for updates and install what it offers. Microsoft says this can install newer drivers for the drive.
3. On a Mac, choose Apple menu > System Settings > General > Software Update and install any update. Install any update from the device maker too, using the maker's own website.

4. Check Windows for the device

1. Right-click the Start button and select Device Manager.
2. Look for an item marked with a yellow warning sign, or an entry named Unknown USB Device, under Universal Serial Bus controllers or Other devices.
3. Right-click that item and select Uninstall device. This may ask for an administrator password. If it asks, do not tick any box to delete driver software unless the device maker says to.
4. Unplug the device, wait a minute, and plug it back in. Windows should install the driver again by itself. You should see the device in File Explorer or the device list.

For a drive, Microsoft also suggests expanding Disk drives in Device Manager, uninstalling the drive entry the same way, unplugging, waiting a minute, and reconnecting. For more on drivers, see fixing driver problems in Device Manager.

5. Turn off USB selective suspend (Windows)

USB selective suspend lets Windows switch off a USB port to save power, and some devices fail to wake. Microsoft lists turning it off as a fix for an external drive that is not recognized. Try it only after the earlier fixes.

1. Select Start and type power plan. Select Choose a power plan (or Edit power plan).
2. Next to your current plan, select Change plan settings, then Change advanced power settings.
3. Expand USB settings, then USB selective suspend setting.
4. Set Plugged in to Disabled. On a laptop, set On battery to Disabled too.
5. Select Apply, then OK. Unplug the device and plug it in again.

6. Check on a Mac

1. Hold the Option key and choose Apple menu > System Information.
2. In the left list, select USB (under Hardware). If your device is listed, the Mac sees it, and the device's own manual or maker is the next stop.
3. On a MacBook with Apple silicon, open Apple menu then System Settings then Privacy & Security then Accessories. If an earlier alert was answered with Don't Allow, change Allow accessories to connect to Ask for New Accessories, then unplug and replug the device and choose Allow. This setting applies to Mac laptops with Apple silicon.
4. Quit and reopen any app that uses the device, then restart the Mac with the device unplugged.

7. Test the device on another computer

Plug it into a different computer. If it works there, the problem is with your computer's port, driver or settings. If it fails on every computer and every cable, the device itself is most likely faulty.

If it still does not work

• On Windows, the maker of your PC may offer a chipset or USB driver on its support website. Download it only from the PC maker's own site, never from a driver-update tool.
• Apple advises that if a port still fails on a Mac after the steps above, the computer may need service.
• For a flash drive or hard drive that connects but has no letter or does not open, see External hard drive not showing up.
• For a phone, see connecting a phone to a computer with USB.

Frequently asked questions