Symptoms
- Drive doesn't appear on the desktop or in Finder
- Drive isn't listed in Disk Utility either
- Drive makes clicking, grinding, or spinning-up-and-down noises
- Drive worked before but stopped being recognized recently
Likely causes
- CommonA loose or faulty cable connectionUSB and Thunderbolt cables can develop internal faults with no visible sign.
- CommonInsufficient power for the drive, especially larger desktop drivesSome external drives need their own power adapter, not just USB power.
- PossibleA drive formatted in a way macOS doesn't support without extra softwareNTFS-formatted drives (common from Windows) can be read but not written to by default on macOS.
- PossibleA failing or dying external driveUnusual noises are a strong indicator of physical drive failure.
- PossibleA corrupted partition table or file systemThis can prevent the drive from mounting even if the hardware itself is fine.
What to do
- Try a different USB/Thunderbolt cable and port, since these are common points of failure.
- Check that the drive has adequate power; use its dedicated power adapter if it has one, or try a different USB port that can supply more power.
- Open Disk Utility (Applications > Utilities) to see if the drive appears there even if not on the desktop, which suggests a formatting or mounting issue rather than a connection problem.
- If the drive appears in Disk Utility but won't mount, try running First Aid on it.
- Test the drive on another computer if possible to rule out a Mac-specific issue.
- Listen for unusual clicking or repeated spin-up/spin-down sounds, which strongly suggest mechanical failure.
- If the drive is NTFS-formatted from a Windows PC, confirm you can at least read from it (writing requires third-party software or reformatting).
- If the drive makes unusual noises or won't appear anywhere, stop using it to avoid further damage and prioritize data recovery if it contains important files.
Tools and parts
- Known-good USB/Thunderbolt cable
Replacement external hard drive/SSDSearch: “external hard drive or SSD”
When to call a pro
If the drive makes clicking or grinding noises, or contains important data you can't otherwise access, a professional data recovery service should be consulted before further attempts.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.