Since Seagate is one of the most popular brands you will find when searching for a backup external hard drive for a Mac on sites like Amazon, we’ll troubleshoot this problem based on one of their hard drives. The first thing you will run across when you search for a read-only external hard drive on a Macis the suggestion to reformat it. My Seagate Backup Plus Slim disk box states it can be used with both Windows and Mac. It worked fine with the Power Mac and also with the Windows machine. However, after I used it on a Windows machine, it appears as Read Only on the Mac. Other than formatting, what can I do to regain write capability with the Mac? The Seagate hard drive read-only mode can be easily changed in a click by using a third-party NTFS reader - EaseUS NTFS for Mac. EaseUS NTFS for Mac is a robust NTFS mounter, which features to change the drive from read-only to read-write mode on the hard drive, external hard disk, SSD, USB drive, Thunderbolt drive, SD card, CF card, etc.
External hard drives, such as those made by Seagate, provide a way to back up important data and media stored on your computer. However, there isn't much point in storing all of this data if you can't access it. That's what happens when a hard drive is set to 'read only' mode. That means you can look at the information stored on the drive, but you can't add or remove data. The good news is you can change your Seagate hard drive from 'read only' without the help of a service technician. All you need to do to is reformat the hard drive.
Access the Start menu on your computer and locate the 'My Computer' or 'Computer' icon. Using the mouse, right-click on the icon and select 'Manage' from the list of options in the window.
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Click 'Disk Management' in the left side of the window. It will be located under 'Storage.' Wait for a new window to appear listing all of the drives currently connected to your computer.
Right-click on the drive listed as 'Seagate' in the list of options and select 'Quick Format' from the list of formatting options.
Click 'OK' when prompted to complete the reformatting of the hard drive. The Seagate hard drive will be completely reset to its factory specifications, and it will no longer be in read-only mode.
Click the 'Finder' icon in the menu bar of your Mac. Click 'Utilities' from the list of options and then select 'Disk Utility' from the drop-down menu. A list of drives connected to your Mac will appear in a window.
Seagate Expansion Drive Mac
Hold down the 'Control' key and click on the drive listed as 'Seagate.' Locate the 'Partition' tab at the top of the window and click on it. Select '1 Partition' from the list of options. Click the 'Option' tab in the window and select 'Apple Partition Map Radio Button.'
Click 'OK' and then click 'Apply.' Click 'Partition' when prompted by the computer. The Seagate hard drive will be reformatted on your Mac and reset to its original settings; it will no longer be in read-only mode.
Seagate Mac Driver