User level: Level 1 (4 points)Hi everyone!
I’m using a mid-2012 MacBook Pro and a Samsung T7 portable SSD connected via USB 3, but I can’t seem to transfer files to it.
Does anyone know what might be causing this? Could you please suggest some troubleshooting steps I can try?
Thanks in advance!
Posted on Oct 25, 2026 5:30 AM
User level: Level 10 (148,617 points)Oct 25, 2026 8:17 AM in response to bulutsenyaprak
Finder and the rest of MacOS deal with mountable Volumes, not bare drives.
If this is the FIRST time you have used this drive, or the first time you have used it on your Mac, you will likely need to initialize/ERASE the drive and create a Mountable Volume on it.
The most common format used by macOS after 10.13 High Sierra and later is GUID and APFS.
If you need to interchange with Windows, some users find exFAT more easily readable on a PC, but somewhat slower on a Mac.
if this is intended to be a Time Machine drive, more recent versions of MacOS automate initializing the drive for Time Machine, Ince you inductee this is the drive you wish to use for Time Machine. I honestly do not know what 10.15 Catalina does.
Initialize an external storage device in Disk Utility on Mac - Apple Support
User level: Level 7 (22,314 points)Oct 26, 2026 12:04 AM in response to bulutsenyaprak
Also DON'T install any Samsung disk management software because it often fails in different macOS versions.
When getting a new drive, just set Disk Utility.app > View > Show All Devices, and then erase the topmost device (not any volumes under it) as GUID, APFS, case insensitive.
User level: Level 10 (87,747 points)Oct 25, 2026 8:12 AM in response to bulutsenyaprak
What format is the SSD? If the SSD is formatted for Windows then your Mac can not write to it. Ensure the SSD is formatted for your Mac.
Originally posted at discussions.apple.com/thread/256382623