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USB device not recognised on your Mac: find the fault

A drive or keyboard the Mac ignores is usually the port, the cable or the hub. System Information tells you within seconds whether the Mac can see it at all.

  • DifficultyMedium
  • Time15 min
  • RiskLow
  • ReversibleYes
  • PlatformmacOS
  • Updated

Written and tested by emdottech

What that means

Low risk. This fix only checks things, or changes settings you can switch back in the same place. This change is reversible — you can return to the previous state without professional help or data loss.

System Information's USB list triage — a device listed pointing at software, not listed pointing at port or cable, and greyed out in Disk Utility needing a mount

What usually goes wrong

  • Never format a drive that will not mount until you have tried it on another computer, because formatting destroys whatever is still recoverable.
  • USB-C ports can behave differently even on the same Mac, so test every port before deciding a device is faulty.

Steps

How to verify the fix

The device appears in System Information under USB and mounts in Finder or works as expected.

If this didn't fix it

If it works on another computer but not this Mac in any port, the ports or macOS need service. If it works nowhere, the device or its cable has failed.

Next stop: the related fixes below, or start a guided diagnosis.

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