Mac's inability to recognize external hard disks are usually caused by connection problems, file system incompatibility or software failure. Solutions include: 1. Check the connection and power supply to ensure that the cable and interface are normal and try to connect directly; 2. Check whether the hard disk is displayed in the disk tool and try to mount manually; 3. Confirm whether the file system is compatible (such as exFAT or FAT32), NTFS requires third-party support, and Linux format requires special drivers; 4. Restart the device or reset NVRAM/PRAM; 5. If the above steps are invalid, it may be a hardware failure. In most cases, the above steps can be used to solve the problem.

Your Mac not recognizing an external hard drive can be frustrating, but it's usually not a lost cause. Most of the time, the issue is related to connection problems, file system compatibility, or minor software glitches — things you can troubleshoot without too much hassle.

Check the Basics: Connection and Power

Before diving into complex fixes, start with the simplest possibilities.

• Make sure the drive is properly plugged in and the cable is working.
• Try a different USB or Thunderbolt port on your Mac — sometimes one port might not be functioning correctly.
• If your external drive uses its own power adapter, make sure it's plugged in and turned on.
• Swap out the cable if possible — faulty cables are more common than you'd think.

Some drives require more power than others, especially larger desktop-style external drives. If you're using a USB hub or a dongle, try connecting directly to your Mac instead.

See If the Drive Appears in Disk Utility

Even if it doesn't show up on your desk, your Mac might still detect it behind the scenes.

1. Open Disk Utility (you can search for it using Spotlight).
2. Look in the left sidebar — if your drive appears there, right-click it and choose Mount .
3. If it doesn't mount, check the status below — it may show errors or indicate if the drive needs repair or reformatting.

Sometimes macOS just fails to auto-mount the drive, but manually mounting it through Disk Utility gets things going again.

File System Compatibility Matters

One common reason your Mac won't recognize an external drive is due to the file system it's formatted with.

• macOS can read NTFS drives (commonly used by Windows) but can't write to them by default. Some third-party apps allow writing, but they're not always reliable.
• If the drive is formatted as exFAT , it should work fine — just make sure it's properly mounted.
• Older drives formatted as FAT32 also work, but they have file size limits that may cause issues.
• Drives using Linux file systems (like ext4) typically won't show up at all unless you install special drivers.

If you see the drive in Disk Utility but it says "Not Mounted" or shows an unfamiliar format, reformatting it for Mac use might be necessary — just be aware this will erase all data.

Restart and Reset When in Doubt

Sometimes, a quick reboot can resolve recognition issues.

• Restart both your Mac and the external drive (if possible).
• If you're using an Intel-based Mac, resetting the NVRAM/PRAM might help.
• On Apple Silicon (M1/M2/etc.) Macs, simply shutting down completely for a minute then powering back on can clear up glitches.

Also, try connecting the drive after your Mac has fully booted up. Plugging it in during startup can occasionally confuse the system.

If none of these steps work, the issue could be hardware-related — either with the drive itself or your Mac's ports. But in most cases, checking connections, verifying disk status, and understanding file system limitations will get your drive recognized again.

Basically that's it.

The above is the detailed content of Why won't my Mac recognize an external hard drive?. For more information, please follow other related articles on the PHP Chinese website!