In Focus: How to Solve The ‘Read Only’ External Hard Drive Problem on Mac

Hard Drive Disk
Quick Fix

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Encountering the issue of not being able to write to or copy from a USB hard drive can be frustrating when using a MacBook.

There isn’t a single solution to all these woes, but here’s a quick guide to addressing these bugbears that involve external hard drive performance and connection to Mac.

File systems: An overview

A file system is a handy tool that allows an OS to read data on any USB drive or hard drive. There are quite a few file systems out there, and the reality is that not every operating system works fine with each one of those systems.

Apple computers use HFS+ file system by default. Windows, on the other hand, uses New Technology File System (NTFS).

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Time Machine Backup From an External Hard Drive

Mac users are likely to find FAT32 and exFAT as their best options, and for a good reason. If you’ve ever tried to format a hard drive as NTFS, you have probably come across a handful of trouble in getting it to work with your Mac or Linux. macOS is able to recognize as well as read NTFS drives, but it cannot write to them. NTFS works flawlessly with Windows, but leaves much to be desired with everything else.

Meanwhile, FAT32 and exFAT work with all operating systems just fine. File Allocation Table (FAT) is the oldest of the file systems, hence it can be recognized by every OS out there. Personal computers have seen its evolution from FAT12 to FAT16 to the current FAT32, and then the arrival of exFAT, created with USB drives and external drives in mind.

Your operating system’s primary hard drive should be the best match for that OS, while USB drives and external hard drives should use either FAT32 or exFAT.

FAT32 vs. exFAT

Here are some points of comparison to help you decide on which one to go with:

  • Devices supported – FAT32 is the most widely compatible file system, working on any OS as well as media players, devices, and video game consoles. exFAT, in contrast, will work fine on 99 percent of devices, but may encounter an issue on certain media players. Xbox One, for instance, usually runs into issues with exFAT USB drives formatted on a Mac.
  • Sizes supported – FAT32 can support files with up to 4 GB in size and can be used as the file system on hard drives that are 8 TB at a maximum. exFAT, however, has no limitations on file sizes as well as hard drive sizes, making it the better option for those who are using a portable drive that stores massive files, such as 3D projects.
  • Speed – Generally, exFAT drives are quicker at writing and reading data compared to FAT32 drives. As a rule of thumb, format your drive as exFAT if you are fairly sure that you won’t have a file smaller than 4 GB.

You can easily format a USB drive or external hard drive as exFAT instead of FAT32. macOS users can follow these steps:

  1. Open Spotlight (Command + Space). Run Disk Utility.
  2. Select the USB drive in the menu found on the left.
  3. Click Erase, and then choose exFAT in Format.

External hard drive ‘read only’ issue? Here’s a quick fix

Once you plug in your drive and open Disk Utility, highlight your drive in the sidebar and click Erase, as shown in the instructions above. Your next step, however, can vary depending on what you want to do with the blank drive:

  • Portable drive – Are you keen on making a portable drive to use with your Mac and Mac computers alone? Format your drive to HFS with the Mac OS Extended option.
  • Time Machine backup – Are you using the drive to back up your Mac with Time Machine? Then format the drive to HFS+, which shows up as Mac OS Extended in the Disk Utility GIU.
  • For older devices – In the off chance that you’re using the disk with another device that doesn’t support for exFAT, then select the older FAT option. Usually you should veer away from this option because it limits drive sizes to less than 32 GB.

Now, let’s get to a one-time fix of enabling macOS built in experimental NTFS support. Take note: this method can have serious consequences and result in loss of data on target drive, so skip this fix if you’re writing to important volumes or eyeing a long-term solution.

This fix is based on the fact that sometimes we need to write some files to a drive once, in which case nothing needs to be installed. Mac has built-in support for reading NTFS by default, with the write capability hiding behind a Terminal hack.

Follow these steps:

  1. Open Terminal. In your editor of choice, open /etc/fstab. If you have no preference, use Nano and type:

nano etc/fstab

  1. Copy this line into the file:

LABEL=DRIVENAME none ntfs rw,auto,nobrowse

  1. Replace DRIVENAME with the name of the drive you’d like to access. Save the file by hitting control+o, and then control+x to quit Nano.
  2. Disconnect and reconnect your drive in order to remount it. Now it’s available in /Volumes. Get here via Finder: in the menu bar, click Go and choose Go to Folder. Enter /Volumes and then click Go.

fstab is a hidden file setting preferences for disks, and can be useful for preventing disk partitions from mounting. In this particular case, it allows you to read-write on a disk that is not writable on default.

If you’re hardly comfortable with Terminal, you can choose a paid option for a pain-free way of working with files. A paid option likely entails less work and, as we mentioned earlier, experimental support isn’t reliable in the long term.


To summarize, a Mac can read from an NTFS disk, but it cannot write to it without a little work and help from third-party NTFS software. You need to format the drive for use on a Mac.

exFat outperforms Fat32 in most aspects. NTFS is better in nearly all aspects compared to exFAT, but only if you are using a USB drive on Windows computers. If you’re a Mac user, NTFS isn’t good news for you.

Once you’ve solved “read only” external hard drive problems on your Mac, get into the habit of cleaning and optimizing your Mac for top performance using a reliable tool such as Mac repair app.

Mac users, tell us about your own experience!

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