Why has my USB port or USB device stopped working?
Nothing happens, or Windows says the device is not recognised. The cross-test that tells you in a minute whether the fault is the port, the cable, the device or the driver — and why so many cables cannot carry data at all.
- Difficulty
- beginner
- Time
- 25 min
- Read
- 6 min
Short answer
Cross-test before anything else: try the device in a different port, and try a different device in the original port. That one minute of swapping tells you which end is broken and stops you replacing the wrong thing. If both fail, suspect the cable — an enormous number of USB cables sold with devices are charge-only and carry no data at all, and they look identical to ones that do.
USB looks like one thing and is several. A socket carries power, data and sometimes video, over cables that may support any combination of those, at speeds that differ by a factor of a hundred between the oldest and newest standards, with connectors that fit each other while doing entirely different jobs. That is why "the USB has stopped working" resolves so often to a cable, a hub, or a port that has quietly been switched off to save power — and why the cross-test matters more here than anywhere else on a computer.
Step by step
- Cross-test the port and the device.Device into a different port; a known-working device such as a mouse or a memory stick into the original port. Four outcomes, each pointing somewhere different: device is faulty, port is faulty, both work and it is a cable or power problem, or neither works and it is the machine.
- Swap the cable, and assume nothing about it.Charge-only cables — usually the ones supplied with headphones, power banks, e-readers and cheap accessories — have no data wires. The device charges perfectly and never appears on the computer. There is no external difference. Use a cable you have seen carry data before.
- Take the hub out of the equation.Plug directly into the machine. Unpowered hubs cannot supply enough current for hard drives, some scanners and some phones, and a hub with several devices on it can starve them all. If it works directly and not through the hub, buy a powered hub rather than blaming the device.
- Try the ports on the back of a desktop.Front-panel ports on a desktop are connected by an internal cable that comes loose, and they often share limited power. The ports on the rear are soldered to the board and are the reliable test.
- Turn off the power-saving setting that disables ports.Windows suspends USB devices to save power and does not always wake them properly. In Device Manager, under each USB root hub's power management tab, there is an option allowing the computer to turn the device off — clearing it on all of them resolves a long-standing family of intermittent faults, particularly on laptops.
- Remove and redetect the controllers.In Device Manager, uninstall the USB controllers under Universal Serial Bus controllers and restart. Windows reinstalls them automatically. It sounds drastic and is routine — it clears corrupted device records, which is the usual cause of one specific device being permanently "not recognised" while everything else works.
- Do a full power drain if every port is dead.Shut down, unplug from the mains, remove a removable battery, and hold the power button for thirty seconds. USB controllers can latch into a fault state after an over-current event — a shorted cable or a failing device — and this is what clears it.
- Consider what the device needs beyond power.A phone must be unlocked and set to file transfer mode before it appears; the catalogue's guide on transferring photos covers that properly. A drive formatted for another system may be connected and healthy but invisible in Explorer — that is the unrecognised drive guide, not this one.
Common mistakes
- Buying a replacement device before cross-testing — The cross-test costs a minute and is the only thing that identifies which end is broken. A large share of "dead" USB devices are working devices on a charge-only cable.
- Assuming a USB-C cable is a USB-C cable — They differ enormously — charge-only, data at various speeds, video or not, and power ratings from a few watts to a hundred or more. The catalogue's guide on identifying a cable by its plug covers reading the markings.
- Running drives and scanners through an unpowered hub — It works until it does not, and the failure looks like a faulty device. Anything with a motor, a lamp or a spinning disc wants either a direct port or a powered hub.
If it doesn't work
"USB device not recognised" every time in every port
Cause: The device, the cable, or a corrupted device record — Fix: Cable first, then uninstall the USB controllers and restart. If a second computer also refuses it, the device has failed.
One port dead, the rest fine
Cause: Physical damage or a loose front-panel connection — Fix: Look into the port with a torch for a bent or pushed-down contact. On a desktop front panel, the internal header may simply have come off.
Works for a while then disconnects, repeatedly
Cause: Power saving, insufficient power, or heat — Fix: Clear the USB selective suspend setting, and try a powered hub. Portable hard drives on laptop ports are the classic case — they draw more than the port comfortably supplies.
Device works on one computer and not another
Cause: Driver, or port power capability — Fix: The device is fine. Look at drivers on the failing machine and at whether the working machine's port supplies more current.
A USB-C device does nothing in a USB-C port
Cause: Not all USB-C ports do all things — Fix: USB-C is a connector, not a capability. Some ports carry data only, some add video, some add power delivery, and the same-looking cable may support only some of those. Check the small icons beside the port.
Everything stopped after plugging in one thing
Cause: An over-current condition latched the controller — Fix: Unplug everything, do a full power drain, and do not reconnect the device that caused it. A cable or device that shorts a port can take out every port on that controller until the machine is fully depowered.
Questions people ask
Can a USB port actually wear out?
Yes, though it takes a lot. Connectors are rated for a few thousand to ten thousand insertion cycles, and the port that takes a memory stick every day for years can develop a loose contact. Leverage damage from a heavy adapter hanging out of a laptop is far more common than wear.
Why is my external drive slower on one port than another?
Ports on the same machine often run at different speeds. Blue-coloured ports are conventionally the faster USB 3 ones, and the fastest ports are usually labelled with an icon showing the speed. Plugging a fast drive into an old black port can make it many times slower.
Is it safe to unplug a USB stick without ejecting?
Usually, since both Windows and macOS now default to write caching that makes it safe most of the time — but not always, and a copy that is still finishing will be lost. The catalogue has a guide on this specific question.
My phone charges but the computer does not see it
Two likely causes: a charge-only cable, or the phone not being unlocked and set to file transfer mode. Android shows a notification asking what the connection is for and defaults to charging only; an iPhone shows a Trust prompt that must be answered.