USB device not recognised
My flash drive is not showing up when I plug it in.
Written by The CommonFixes team · fact checked by CommonFixes review desk
Last updated
Short answer
Either the port is not supplying power correctly, or the drive has no letter assigned to it, which makes it invisible while still being connected. The quickest thing to try first: try every port and another computer — Test the front and back ports, and avoid unpowered hubs. Trying the drive on another computer tells you instantly whether the drive or the computer is at fault. Most people are done in about 15 minutes.
Full walkthrough below: 5 steps for Windows and Mac, rated easy.
Sounds like this
- •USB device not recognised message
- •Drive missing from This PC
- •Light on the drive is off
Why it happens
Either the port is not supplying power correctly, or the drive has no letter assigned to it, which makes it invisible while still being connected.
Work through these in order
0% done- 1
Try every port and another computer
Test the front and back ports, and avoid unpowered hubs. Trying the drive on another computer tells you instantly whether the drive or the computer is at fault.
- 2
Look in Disk Management
Right click the Start button, choose Disk Management, and look for a drive with no letter. Right click it, choose Change Drive Letter and Paths, and assign one.
- 3
Reinstall the USB controllers
In Device Manager expand Universal Serial Bus controllers, uninstall any entry marked with a warning triangle, then restart.
- 4
Turn off USB power saving
In Device Manager open each USB Root Hub, go to Power Management, and untick allowing the computer to turn it off.
- 5
Clean the connector
Pocket lint packed into the port is a genuine and very common cause. Switch off and clear it out gently with a wooden toothpick.
If none of that worked
If Disk Management shows the drive as unallocated, the files need recovery software before you format it.
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Who wrote this and how we checked it
The CommonFixes team
Writer and researcher
We are a small group of people who spend our days repairing laptops and desktops for family, friends and small offices. Every guide here starts with a problem someone actually brought to us, and we only write down the steps that put the machine right.
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- Windows and Mac
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CommonFixes review desk
Technical editor
Before a guide goes live, a second person walks through it on a real machine and checks each instruction against the maker's own support pages. Anything we cannot confirm is removed rather than guessed at.
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This guide was last updated on 10 August 2026. If a step no longer matches what you see on screen, tell us on the contact page and we will test it again.
A gentle reminder: back up anything you cannot afford to lose before major repairs. If a step ever feels risky, stop and ask a technician. There is no shame in that.