How to Fix Mac Not Recognizing External Drive

Fix external drive detection issues on Mac with these proven troubleshooting steps. Resolve USB, Thunderbolt, and drive mounting problems quickly.

1. Check the physical connection. Unplug the external drive and reconnect it firmly to a different USB or Thunderbolt port on your Mac. If using a USB hub, connect the drive directly to your Mac instead. For drives requiring external power, verify the power adapter is connected and the drive's LED indicators show it's receiving power.
2. Test with Disk Utility. Open Disk Utility from Applications > Utilities or press Command + Space and type "Disk Utility". In the sidebar, click View > Show All Devices to display hidden drives. Look for your external drive in the list, even if it appears grayed out or unmounted.
3. Reset the SMC and PRAM. Shut down your Mac completely. For Intel Macs, hold Shift + Control + Option on the left side plus the power button for 10 seconds, then release. For Apple Silicon Macs, simply restart the computer. After startup, hold Command + Option + P + R until you hear the startup chime twice to reset PRAM.
4. Run First Aid on the drive. In Disk Utility, select your external drive from the sidebar and click First Aid in the toolbar. Click Run to scan and repair any file system errors. Allow the process to complete even if it takes several minutes for larger drives.
5. Check file system compatibility. Select your drive in Disk Utility and note the format listed in the information panel. NTFS drives from Windows PCs are read-only on Mac by default. If you need write access, reformat the drive to exFAT or Mac OS Extended, understanding this will erase all data on the drive.
6. Test on another computer. Connect the external drive to another Mac or PC to determine if the issue is drive-specific or Mac-specific. If the drive works on other computers, the problem lies with your Mac's hardware or software configuration rather than the drive itself.
7. Update macOS and check System Information. Click Apple menu > About This Mac > Software Update to install any pending macOS updates. Then open System Information by holding Option and clicking Apple menu > System Information. Under Hardware > USB or Thunderbolt, verify your Mac detects the connection even if the drive doesn't mount.