Use the mouse pointer or the arrow keys on your keyboard to select the disk called Install macOS Catalina in the drive list that appears on the screen. Once the USB drive has booted, select Disk. Step 1: Go Utilities Disk Utility. Step 2: Click the icon of unmountable USB flash drive on the left part of the window. Step 3: Click the Erase button on the top of the Disk Utility window. Step 4: Complete the related information (name, format, scheme), then click Erase button.
Summary: Don't know how to fix when USB flash drive is not mounting on Mac? Try these 4 solutions in this page and use iBoysoft Data Recovery for Mac to recover lost data necessarily.
- Table of contents
- 1. Why the USB flash drive is not mounting on Mac?
- 2. How to fix/repair “USB flash drive not mounting” issue on Mac?
- 3. How to recover lost data from unmounted/unrecognizable USB flash drives?
When I plugged in my USB flash drive on macOS High Sierra, I can't see it in Finder or on the Desktop. So, I went to Disk Utility, it was there. But the USB flash drive was grayed out in Disk Utility and I could not mount it. How can I fix/repair USB flash drive not mounting issue on Mac?
It is user-friendly that Mac will automatically mount the inserted USB flash drives. However, if the USB flash drive is not mounted on Mac, you will lose access to the USB flash drive as well as to the data stored on it. But don't worry, this page talks about the reasons for this issue, and how to fix 'USB flash drive not mounting on Mac' without data loss even if external hard drive is not showing up on Mac.
Why the USB flash drive is not mounting on Mac?
What makes the hard drive not working problems like USB flash drive unmounted on Mac can be various. This is because that this external drive is connected to the Mac computer through USB cable, USB port and many other components. The possible reasons for this issue include:
- Faulty connections like broken cable and wobbly USB port
- File system errors, volume header corruptions, etc. in the USB flash drive
- Disk Utility failure, log file corruption, OS malfunction on this Mac
- Physical damage and other factors
How to fix/repair USB flash drive not mounting issue on Mac?
No matter what results in unmountable USB flash drive, it's urgent to fix/repair USB flash drive not mounting issue on Mac. Here are 4 solutions to this unmounted USB flash drive issue according to different causes, you can check them one by one.
Solution 1: Check the USB flash drive in System Information
If you plug this USB flash drive into your Mac computer but get no sign that this drive is mounting on Mac, you can check System Information to see if this USB flash drive is showing up.
- Step 1: Go to Utilities and choose System Information.
- Step 2: Double-click on its icon to open it and choose USB in the left sidebar.
- Step 3: Check if your USB flash drive is detected by the system in the right box.
If your USB flash drive is not showing up in the right box, you can try to re-plug it, or change another USB port and cable to connect it.
Solution 2: Check the Finder Preferences
Sometimes, you just can't find the USB flash drive in Finder and on the desktop, but actually, it is mounted on your Mac and just not showing up. Check the Finder Preferences and see if it will appear.
- Step 1: Click Finder and choose Preferences in the top menu bar.
- Step 2: Check External Disks in General tab so that the USB flash drive can be shown on the desktop.
- Step 3: Go to Sidebar and check External disks so that they can be located in Finder.
Solution 3: Check and repair this USB flash drive with Disk Utility
If you still can't access your USB flash drive thereafter, you can go to Disk Utility which is a built-in utility to fix disk problems. If it is greyed out in Disk Utility, you can manually mount this USB flash drive.
- Step 1: Go > Utilities > Disk Utility.
- Step 2: Click on View option and choose 'Show all devices'.
- Step 3: Click on the name of your USB flash drive.
- Step 4: Select Mount in the upper menu bar.
If the Mount button is greyed out and you can't mount this USB flash drive manually, then there could be some disk errors. Fortunately, you can use First Aid in Disk Utility to repair this unmountable USB flash drive.
Mac Os Catalina Flash Player
- Step 1: Launch Disk Utility.
- Step 2: Choose the grayed-out USB flash drive.
- Step 3: Select First Aid in the top center and click Run.
Solution 4: Fix the unmountable USB flash drive by reformatting
However, if Disk Utility fails to repair this external drive because of serious file system corruption, you can only fix this by reformatting. The thing you need to keep in mind is that reformatting will erase all files on this USB flash drive, which means, you need to make sure an existing file backup. Or you can recover lost data from the unmountable USB flash drive before you fix the USB flash drive not mounting issue on Mac by reformatting.
How to recover lost data from unmounted/unrecognizable USB flash drives?
Can't open the unmountable USB flash drive but don't want to lose data? You can still get your files back with USB flash drive data recovery software before you reformat this drive.
As one of the most professional USB data recovery software, iBoysoft Data Recovery for Mac is highly recommended. It can recover lost data from unmountable, unreadable, and corrupted USB flash drive, recover deleted/lost files from emptied Mac trash. Moreover, this software performs well in recovering data from hard drives, external hard drives, flash drives, USB sticks, SD cards, and other storage devices. Data recovery is allowed on macOS 10.14/10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8/10.7.
Step 1: Recover lost data from unmountable USB flash drive with Mac data recovery software
- Step 1: Download and install iBoysoft Data Recovery for Mac on your Mac.
- Step 2: Connect your USB flash drive to the Mac and launch iBoysoft Data Recovery for Mac.
- Step 3: Select the unmountable USB flash drive and click 'Next' button to scan all lost files.
- Step 4: Preview the scanning results by double-clicking, choose files that you want to recover, and click 'Recover' button to get lost data back.
Note: In case you lose the recovered files again in the next reformatting step, you'd better save these files to another reliable drive.
Step 2: Reformatting this USB flash drive without data loss
After recovering data from this unmountable USB flash drive, you can reformat this USB flash drive without worrying about losing anything important.
- Step 1: Go > Utilities > Disk Utility.
- Step 2: Click the icon of unmountable USB flash drive on the left part of the window.
- Step 3: Click the Erase button on the top of the Disk Utility window.
- Step 4: Complete the related information(name, format, scheme), then click Erase button.
When the process finished successfully, your USB flash drive will be mountable on the Mac computer again. But the case is, no matter how powerful USB flash drive data recovery software is, the best way to recover files from external drives is to recover them from backups. So, remember to duplicate your files this time.
You may also want to know:
HSD not mounting or seen in Disk Utility? Tutorial to fix SD card not mounting on Mac and recover lost data from unmountable SD card on macOS.
Nowadays, when you buy a USB drive, you can use it right out of the box with your Mac. However, unless it’s been designed for use with a Mac, it won’t be formatted using macOS’ preferred file system (either Mac OS Extended or APFS, depending on which version of macOS you’re running).
That’s because most of the computers in the world run Windows, and Windows uses a different file system, usually one known as Fat32. Drives formatted as Fat32 can be read from and written to by macOS, but it’s not optimal and you’re more likely to run into problems than if you use macOS’ native format. So, if you’ve bought a USB drive that’s formatted as Fat32, or any other format other than Mac OS Extended (also known as HFS+) or APFS, here’s how to format a USB drive on Mac. It’s exactly the same procedure if you need to reformat a flash drive on a Mac.
How to format a USB drive on a Mac
1. Plug the drive into a USB socket (if you have a recent MacBook or MacBook Pro that only has USB-C connectors, you’ll need a USB-C to USB-A adaptor).
2. Open a new Finder window and click on the drive. Make sure it has no files on it that you need. The process of reformatting it will wipe all the data from it.
3. Once you’ve copied any files you need from the USB drive to your Mac, go to Applications>Utilities and double-click on Disk Utility.
4. Click on the USB drive in the sidebar and then choose Erase from the toolbar at the top of the window.
5. In the window that drops down type a name for the formatted drive in the box next to Name.
6. Choose a format from the dropdown menu.
7. If you have previously stored sensitive data on the drive, click the Security tab.
8. Choose a security level using the slider. The further to the right you move the slider, the more ‘passes’ the erase tool will make and the more securely files will be deleted. However, it also increases the time it takes to format the drive quite considerably.
9. Click Ok then click Erase.
Tip: You don’t need to erase a whole drive to delete files securely. If you have confidential files or sensitive data you need to remove from your Mac completely, you should use CleanMyMac’s File Shredder. It’s specifically designed to securely delete sensitive data and will render it unrecoverable. You can download CleanMyMac X for free here.
Which format to choose?
If your Mac is running macOS High Sierra or later, you have two options for file formats: APFS and Mac OS Extended. Which should you choose? The key point is that disks formatted as APFS won’t be recognized by Macs running versions of macOS older than High Sierra. So if you think you might need to plug the USB drive into a Mac running an older version of macOS, format it as Mac OS Extended.
APFS is optimized for SSD (solid state drive) such as flash drives, so if you reformat a flash drive on a Mac, you should definitely choose APFS (unless you plan to use it with a pre-High Sierra Mac, of course). Even on hard drives, however, APFS is faster and more reliable than Mac OS Extended.
Mac Catalina Iso
Finally, if you plan to use the USB drive as a destination for Time Machine backups, choose Mac OS Extended. Time Machine can’t currently back up to an APFS disk and if you select one for use with Time Machine, it will offer to reformat it as Mac OS Extended. You can, however, backup an APFS formatted disk to a Mac OS Extended Time Machine drive.
How to format a USB drive to FAT32 on a Mac
The main reason for formatting a USB drive as Fat32 on a Mac is that you want to be able to use the drive on a Windows PC, as well as a Mac — perhaps to transfer files between the two machines. You may also be preparing the drive for use as, say, a storage device for a media player or to record TV programmes on a TV with a USB port.
The fact that Fat32 can be read from and written to on both Mac and Windows makes it very versatile. However, there is a significant limitation — individual files have a maximum size of 4GB. So, if you’re using the USB drive to store large video files, you may run into trouble. There is a solution, however, exFAT. Unlike FAT32, exFAT doesn’t have a maximum file limit. Better still, it can be read from and written to on any Mac running Mac OS X Snow Leopard or later and on Windows.
To format a USB drive in FAT32 or exFAT:
1. Plug the USB drive into your Mac.
2. Go to Applications>Utilities and launch Disk Utility.
3. Click on the USB drive in the sidebar in Disk Utility.
4. Click Erase in the Disk Utility toolbar.
5. Type in a name for the formatted disk.
6. Click on the Format menu and choose either MS-DOS (FAT32) or ExFAT.
7. Click Erase.
Your USB drive will now be erased and re-formatted as either FAT32 or ExFAT, depending on the format you chose in step 6.
How to manage your drives easily
If you look for a quick and easy way to manage your drives, try using CleanMyDrive 2. With its help, you can drag-and-drop files directly to any drive, clean hidden junk from external drives, and check disk stats. It works for all drives, including USB drives, SSD, SD cards, external hard drives. All the drives will be at hand in the menu bar, so you can get to see types of drives you have and manage them easily. CleanMyDrive is absolutely free to use, so download it on the Mac App Store and enjoy!
It’s very easy to format a USB drive on a Mac using Disk Utility. There are a couple of things you should keep in mind, however. The first is that when you format and disk, you will erase all the data currently on it. So if you need that data, make sure you copy it onto another disk before you start. Secondly, there are several formats to choose from, each with advantages and disadvantage. Use the guide above to help you decide which is right for you.