How to Fix a Corrupted/Unreadable Flash Drive on Mac and Get Back Your Data

Have you noticed issues with your USB drive? Is it throwing errors when you try to open files? Maybe some files have mysteriously disappeared, or worse, your Mac doesn’t recognize the drive at all. These are all classic signs of drive corruption, and believe us—we’ve seen it all. Over the years, we’ve helped tons of people tackle this exact problem. Luckily, there are a couple of solid ways to fix a corrupted flash drive on a Mac, and we’re here to walk you through the process step by step.

Step 1: Check Disk Utility for Drive Visibility

The first step is to see if your Mac recognizes the drive at all. Even if it doesn’t show up in Finder, Disk Utility can help you find out if the drive is at least detectable. Disk Utility shows every storage device connected to your Mac, so it’s a fast way to check the drive’s status.

1. Open Disk Utility. Go to Applications > Utilities > Disk Utility to get started.
2. Look for your flash drive under External in the sidebar. If you see it here, it means your Mac recognizes the drive, even if you can’t fully access it.
3. If the drive shows up but isn’t mounted, select it and click Mount at the top of the window. This tries to make the drive accessible in Finder, which might let you open and access files.
4. Take note of any error messages. Disk Utility may show an error if it can’t mount the drive. This feedback could be useful as you move through the next steps.

Step 2: Backup Your Files from the Drive to Your Mac

Before you try any repairs, back up any files you can still access on the drive. Some repair steps could mess with the data, so backup will make everything safer. But what if you can’t access the drive in Finder? Or what if it doesn’t even show up? In that case, you can use specialized data recovery software, that can pull files even from corrupted USB drives.

You’ll find tons of data recovery apps online, but not all of them fit the bill. Here’s what to look for in a tool that can handle your situation:

• Pick a tool that can handle the file systems you typically see on USB drives, like FAT32, exFAT, NTFS, and APFS. This way, it can read your data, no matter the drive’s format.
• A good recovery app offers a few types of scans, each aimed at different issues:
  • Quick Scan: Fast and useful for recently deleted files or minor problems, but it’s not very thorough.
  • Deep Scan: Digs into the drive to find files on more seriously damaged or corrupted drives; this one takes more time but gets more results.
  • Signature Scan: Ignores the file system and searches by file type (like JPEGs or PDFs), which works well when the file system itself is too damaged.
• Look for a tool that can create a disk image of your USB drive. This lets you work from a copy instead of the original drive, which lowers the risk of more damage while you recover data.
• Make sure the software works with macOS, especially the latest versions like Sonoma and Sequoia. Lots of recovery apps online haven’t been updated in years, so check that it’s built for your Mac’s OS.

With these points in mind, a couple of tools stand out: Disk Drill and UFS Explorer. You can check out these and other options in our list of the best data recovery apps for Mac. Personally, we’d go with Disk Drill—it consistently gets great recovery results, and unlike UFS Explorer, it’s super easy to use, so anyone can jump in without any hassle.

How to Create a Backup Image of Your Corrupted USB Drive

The Backup feature in Disk Drill, called Byte-to-Byte Backup, creates a complete image of your USB drive. This image includes everything—existing files, damaged files, deleted files, and any data left on the drive.

Here’s how to create a backup image with Disk Drill:

1. Go to Disk Drill’s official website, download the app, and install it on your Mac. The free version lets you preview recoverable files, which can be helpful if you’re evaluating your recovery options.
2. Launch Disk Drill and plug in your corrupted USB drive. Even if Finder doesn’t recognize the drive, Disk Drill should still detect it as long as it’s connected to your Mac.
3. In Disk Drill, find your USB drive in the list of devices. Select it, then click on Byte-to-Byte Backup.
4. Disk Drill will prompt you to choose a location for the backup image. Pick a safe spot on your Mac’s internal storage or an external drive.
5. Click Create backup to start.
6. After the backup is complete, go back to Disk Drill’s main screen (click on 🏠 to return). Select Attach disk image, choose your backup file, and mount it in Disk Drill. Now, you can scan and recover data from the image itself, without touching the original drive.

How to Recover Files from the Backup Image

Now that you have this backup image, no matter what happens next, you’ll be able to recover files from it just as they were when you created it. It’s like having a snapshot of your USB drive at that moment. You could go ahead and scan the original drive itself—maybe things aren’t as bad as they seem—but we can’t know that for sure. That’s why we always recommend to make a backup and scan it instead. Just to be safe.

Here’s how to go through the recovery process from here:

1. Now that you see your created disk image in Disk Drill’s main screen, click on Scan for Lost Data. This will start the process.
2. Click on Search for lost data. Disk Drill will automatically run Quick, Deep, and Signature Scans in sequence to maximize your chances of finding lost files.
3. Once the scan completes, click Retrieve found items at the top of the interface.
4. You’ll see a list of files categorized into groups: Existing files (these are the files that should be fully intact on the backup image), Deleted or lost (includes files you deleted in the past but that haven’t been fully overwritten yet. Disk Drill can recover them if they’re still there in part or whole), and Reconstructed (Disk Drill attempts to rebuild these files if the structure is too damaged).
5. You’ll see Recovery chances next to each file with tags like High, Average, or Low.
6. You can pick and choose what you want to retrieve, or simply select everything.
7. Click Recover, then select a safe destination for the recovered files.

Step 3: Use First Aid to Repair the Flash Drive on Your Mac

Now that you’ve created a backup and recovered any important files, it’s time to try fixing the USB drive itself. Disk Utility’s First Aid tool can find and fix basic file system errors on your drive. It’s usually the first repair option to try for a corrupted drive on macOS.

Here’s how to run First Aid to fix a corrupted flash drive on a Mac:

1. In the sidebar under External, find and select your USB drive. Double-check that you’ve chosen the correct drive to avoid any accidental repairs on other devices.
2. At the top of the Disk Utility window, click First Aid. A prompt will pop up explaining that First Aid will scan for errors and attempt to fix them.
3. Click Run to start. Disk Utility will scan the drive for any errors. You’ll see a progress bar, and Disk Utility will notify you if it finds any problems and whether it can fix them.

Once the scan is complete, Disk Utility will show a message with the results. If it found and fixed issues, try to access your USB drive in Finder to see if it’s now okay.

If First Aid can’t repair the drive, the issue might be more serious—such as severe file system corruption or hardware problems. At this point, we can move on to more advanced repair options.

Step 4: Use Terminal to Repair the USB Drive on Your Mac

If Disk Utility’s First Aid didn’t do the trick, Terminal offers a more advanced way to troubleshoot. Terminal commands can sometimes fix problems that Disk Utility can’t handle. In this step, we’ll cover two repair options: using the repairVolume command directly and, for more complex partition issues—TestDisk app.

Option A: Repair USB Drive on Mac using Terminal Commands

Terminal is a command-line tool on macOS that lets you interact directly with the system. While it might seem technical, Terminal is straightforward once you get used to it, and it can handle issues that standard tools might miss.

Here’s how to open Terminal and use it to repair your USB drive:

1. To open Terminal, go to Applications > Utilities > Terminal. You can also open it quickly with Spotlight Search (press Command + Space, type “Terminal”).
2. Terminal lets you run specific commands to make changes directly to the system. You type a command, press Enter, and Terminal runs that command. First, type diskutil list and press Enter to execute it.
3. This command shows all connected drives and their identifiers (like /dev/disk2). Look for your USB drive by name, size, or details, and note its identifier.
4. Once you’ve identified your USB drive, type the following command (replace diskX with your USB drive’s identifier), then press Enter:
   sudo diskutil repairVolume /dev/diskX
5. You may be prompted to enter your Mac’s admin password. Terminal will try to repair the drive and show you updates as it works. If it finds and fixes errors, it will let you know.

After the repair, open Finder and check if your USB drive is now accessible. If the repair worked, you should see your drive and be able to use it.

📌 Note. We’ve seen cases where the problem wasn’t with the USB drive itself but with the way macOS manages USB connections. You can restart the USB daemon, which handles USB device connections, to fix this issue. To do this, open Terminal and type sudo launchctl stop com.apple.usbd, then press Enter. Next, type sudo launchctl start com.apple.usbd and press Enter again. Unplug your USB drive, wait a few seconds, then plug it back in to see if it’s recognized.

Option B: Repair USB Drive Partition Issues with TestDisk on Mac

TestDisk is a free, open-source tool designed to recover lost partitions and fix file system issues, especially in cases where viruses or human error (like accidentally deleting a partition table) have caused problems. While TestDisk is powerful, it’s not the easiest tool to use—it only works through the command line in Terminal, so there’s no graphical interface. But for complex cases that regular repair tools can’t handle, TestDisk can work wonders.

Here’s how to use TestDisk to fix an unreadable USB flash drive on a Mac:

1. Head to the TestDisk website to download the Mac version, and follow the site’s instructions to install it on your Mac.
2. Open Terminal, navigate to where TestDisk is installed (for example cd ~/Desktop/testdisk-7.2
   ), and type:
   sudo ./testdisk
3. Press Enter, and enter your admin password if prompted to start TestDisk with the necessary permissions.
4. TestDisk will show a list of drives connected to your Mac. Use the arrow keys to highlight your USB drive, then choose Proceed.
5. TestDisk usually detects the partition table type automatically. If you’re unsure, the default option should work. Confirm the detected type and press Enter.
6. Follow the prompts to Analyze the drive; this scan checks for any lost or damaged partitions.
7. After that, TestDisk will show options for recovering or repairing partitions based on what it found. Carefully follow the instructions to restore lost partitions or repair the file structure. Since it’s all command-line based, take your time to make sure you select the right options for your situation.

When you’re done with TestDisk, open Finder to see if your USB drive is now accessible. If TestDisk successfully repaired the drive, it should show up and be ready to use.

Step 5: Nothing Worked? Format the USB Drive

And finally, if nothing else has worked and the flash drive is still giving you trouble, you can format it. Formatting is usually the last and most effective way to fix non-physical issues with USB drives. This process completely erases all data and sets up a new file system, which gives your drive a fresh start. You’ll need Disk Utility for this step, which you’re already familiar with.

Here’s how to format your USB drive on Mac:

1. In Disk Utility, locate and select your USB drive.
2. At the top of the Disk Utility window, click Erase. A dialog box will appear where you can rename the drive and choose a format.
3. Choose a Format and type a name for the drive in the Name field to make it easier to identify later.
4. Click Erase to start formatting. Disk Utility will erase everything, set up a new file system, and remount the drive once it’s done.

Once Disk Utility finishes, open Finder to see if your USB drive is accessible.

Parting Advice

We’d say these 5 steps fix USB issues for about 9 out of 10 drives. But there are, unfortunately, some cases where the drive is just too damaged. When a USB drive is severely corrupted, none of the at-home methods or tools can help. If you have very important data on the drive, the best option in these situations is to contact a professional data recovery service.

Professional recovery services have specialized equipment and techniques that can handle serious damage, including physical repairs to the drive’s components and advanced methods to extract data. However, data recovery from a USB drive can be pricey—often more expensive than a new drive itself. But if the data is truly irreplaceable, professional service is often the last, and sometimes only, solution.