Sequoia 15.4 update made usb drives read only

Then I would recommend running DriveDx (free trial period) as suggest by some of the others to check the health of that drive. Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar. You will need to install a special USB driver in order to access the health information on the external drive. Even new drives can be bad.

I know a couple of people have reported resolving recent external drive issues by connecting the drive to a USB3 hub instead of connecting the drive directly to the computer. I would also recommend disconnecting all other external devices while troubleshooting just in case one of them is causing a problem.

Also make sure to try using a different high quality USB-C USB3/4 cable (or Thunderbolt 3/4) cable from a well respected manufacturer. Many people resolve external drive issues by using higher quality cables from respected manufacturers. Same thing goes if you need to use any adapters. The cables supplied by the drive manufacturers are usually of poor quality.

And of course try each other USB-C port on the Mac.

jameefromspringfield wrote:

This is the error I get when I unmount the disk and attempt to erase and format as APFS:

Erase the whole physical drive instead of just the current volume. This will recreate the partition table on the drive and create a clean APFS Container & volume as well. See this Apple article for details since Disk Utility now hides the physical drives from view by default.

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

This is what everyone should do the first time they use any new external drive. Many times the partition table & formatting from the factory can be problematic & may contain things that can cause problems with some systems. Plus these days there are so many fake drives out there, that erasing the drive like this may reveal the fake right away.

Almost all drives come formatted for Windows. They bundle software that allows macOS to write to the drive. The software is often garbage and breaks at every macOS update.

In Finder, Get Info on the drive. Next to Format if it says NTFS, contact the manufacturer for updated software. Or, better yet, copy the data to another drive, then format the drive APFS IN Disk Utility.

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Hi Jamie, I raised a query with apple support for the exact same issues. The chap was extremely helpful and remoted into my iMac. We successfully erased my external hard drive (WD Passport) and reformatted the disk in APFS format. He waited until the back up started to ensure all was ok.

Hope this helps.

You need to update the proprietary third party software that you are using to manage these external drives. If that does not work, then you need to contact the manufacturers of those drives (or the proprietary software you are using to manage the drives) for assistance.

Otherwise, follow @Barney-15E's advice and use one of three macOS built-in file systems (APFS, HFS+, exFAT).....which one depends on the drives and what other systems need access to those drives.

To resolve this, discuss this issue with the people supporting the NTFS app y'all are using, or offload the current NTFS volume contents somewhere and reformat it as a supported format and reload the contents. Or both.

jameefromspringfield wrote:

My drive is formatted in APFS according to my revised screen capture and it’s still read only. Has been APFS for at least a year and a half.

Yeah, i was viewing the thread and saw your posting showing NTFS, and didn’t see the reversal.

Use DriveDx to see if there are any errors, and if there are any errors shown, replace it.

If no errors are shown, offload the APFS volume, reformat it as APFS, and reload it.

BDAqua wrote:

Read Only may mean the drive is failing test with DriveDX

Certainly possible, though NTFS is natively read-only on macOS, absent a functioning NTFS add-on app.

Read Only may mean the drive is failing test with DriveDX

Are you choosing Show all Devices, then selecting the top unit of that drive?

I spoke with Apple Support and they acknowledged this is a known issue and their dev is working on it.

I cannot see how how 15.4 would cause this. Are you sure you do not have some software that came on the drive that secures the drive?

Hello, I have the same problem since the update :(

With a Lacie drive. I never had any issues before and it is properly detected, but it's in read-only mode and no matter what I try, I can't use it... I connect it as usual to my Windows, and it works perfectly. I don't know what to do anymore. Have you found a solution?

Don't think so. I have been using the WD Passport for Mac since iMac was purchased (M1 chip). Can't see why 2 days ago backing up ok and then did update and now won't back up as 'says disk read only' I checked the permission: as below. not sure what wheel means- guessing system is me. It's odd my other WD passport for Mac has my name as opposed to system. Thanks though

This issue happened to me too. I've had my external drive plugged into my M2 Mac mini for a while now. Two days ago, when copying items to the drive I get an read only message. I remote into the Mac and there's a toast notification at the top that says the drive was not ejected properly. I hadn't remoted into the mini in about six months.

When I look at the Get Info on the drive it now says "You can only read" and I'm unable to create files or folders or copy anything to it. When I try to change permissions on any of the accounts I get a message that the operation failed and that I do not have sufficient privileges. My account is administrator.

I purchased a new drive and formatted it in APFS and it shows the same thing. I know the drives aren't bad because I can format them into NTFS and copy, delete and move files on and off these drives in Windows without an issue.

All of this despite my drives being formatted in APFS. I've never used NTFS or any other format. So now I'm kind of stuck and don't know how to proceed. I've been through every permutation of troubleshooting I can try and nothing works. I've done too much to recount it all but it's been quite frustrating.

The screen captures say the drive was modified January 1 2025 but that's not true. I just reformatted today, May 9th, 2025.