Why isn’t your Mac recognizing an external hard drive?

⚡ Fast fix

• Restart your Mac—it clears a surprising number of drive glitches.
• Reseat the cable and try a different port right away.
• Open Disk Utility and see if the drive needs to be mounted.
• If it’s grayed out, run First Aid before assuming it’s dead.

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When you plug an external hard drive into your Mac, it should appear in Finder®. But what if you can’t see the drive or access any of its files? If your Mac is not recognizing an external hard drive, there are a few possible causes. 

And at Asurion, we’ve seen it all. Our experts have learned from experience how to solve all sorts of tech issues, and we’re here to walk you through it. Try these fixes to get your Mac to connect to your hard drive again. 

Check and mount your external drive

Your external hard drive might be failing because it’s not mounted properly. Mounting the drive makes it accessible on your Mac. That way, you can save and access files on the external drive, like when you have a full Mac startup disc. 

With your external drive plugged in, follow these steps to try to solve your Mac external drive issues:

• Open Finder.
• Go to Applications > Utilities > Disk Utilities. 
• Select View > Show All Devices. 
• Check to see if your drive shows up in the sidebar. 
• If you see your drive but it’s grayed out, click on it and select Mount. 
• If you still can’t access the drive, select First Aid to have the program check and repair minor disk errors.

If you suspect your computer is the issue, consider a force quit on a Mac for any applications you have open. Then, you can perform a factory reset on a Mac to hopefully address serious software issues that could prevent your external drive from connecting properly. Just keep in mind that a factory reset is a drastic step, as it will erase all data on your Mac, including your files and apps. 

Power and connection issues

When an external hard drive is not being recognized on Mac, the connection or power could also be the root cause. On many drives, you’ll see a light to show power and data activity. If you don’t see the drive light up when you plug it in, your drive may not be receiving enough power.

One tip is to transition to a powered hub if you suspect your USB port isn’t supplying enough power. Power issues can prevent external drives from mounting, so check how much power your drive requires and how much your ports supply. 

Do some process of elimination to help diagnose the issue when your computer is not recognizing an external hard drive on Mac:

• Swap out the cables or adapters you’re using to rule out hardware compatibility issues. If the drive works with the new cables, you’re good to go. 
• Test the drive on another computer for comparison. If the hard drive works with another computer, a compatibility issue with the drive formatting could prevent it from connecting to your Mac. 
• Try a different port on your Mac. Plug the external drive into a different port to make sure the port you were using isn’t faulty. 

When hardware might be the problem

The drive itself could be the problem when your external hard drive is not showing up on Mac. Dealing with a failing Mac hard drive can be tricky. Keep an eye out for these signs of drive or enclosure failure.  

• Clicking, whining, or grinding noises coming from the drive
• Files that disappear or become corrupted
• Very slow file access or freezing
• Drive overheating
• A connection that drops in and out
• No light or power to the drive

If you noticed any of these signs recently before your Mac failed to detect the drive, it’s likely that the hardware is the problem. Data recovery software may help you recover your files if your drive is visible but not readable. You may want to consider taking your external hard drive for professional data recovery services if the data on your drive is essential, and you suspect the drive's hardware has failed. 

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FAQ

Why won’t my Mac recognize my external hard drive?

Common causes include unmounted drives, faulty cables, insufficient power, incompatible formatting, or hardware failure.

How do I mount an external drive on Mac?

Open Disk Utility, select the drive, and click Mount if it appears grayed out.

What if my external hard drive is not showing up in Disk Utility?

Try a different cable, port, or computer. If it still doesn’t appear, it may not be receiving power or could have hardware damage.