the memory chip wore out, as is the fate of all of our solid state memory stuff, but more likely to happen years down the road). If you see a warning that says the device is only being mounted in read-only mode while connecting, your hard disk is diagnosed to have formatting errors that prevent you from writing files to it.
#WHY IS THE EXTERNAL HARD DRIVE READ ONLY MAC#
If any important data is in the USB/external hard drive when external hard drive shows up in Disk Management but not File Explorer, you can employ data recovery to retrieve your data before formatting it. Another common cause for the external hard drive Read Only problem on Mac is the formatting errors of the storage device itself. In this state, you can't format it, or do some fun "sudo dd if=/dev/zero of=/dev/disk4 count=1024" type thing it's simply stuck with whatever you last wrote to it (but can probably be read from forever) so, I'm guessing my couple months old USB just crapped out like an old solid state that was well written to, which can happen to new stuff (i.e. When external hard drive issue occurs, an external hard drive is not showing files though they still exist. Open the Disk Utility and click on your external hard drive from the left side devices. Use the Disk Utility feature to check for any hard drive errors that may cause the external hard drive read only issue. SO, I plugged it into a windows machine, ran "diskpart", "select disk 1" (or "list disk" to be sure the disk number!), then "attributes disk clear readonly" (and "exit"), but nope, still a read only disk (whether using windows or mac) Tick the box for ignoring ownership on this volume. Me too (using a 16GB usb stick) I could write to it for a couple months (nothing excessive), but then today is went mysteriously to read-only