Almost of us utilise some kind of external storage device with our Mac at some time or some other, whether it's a USB stick, wink bulldoze, external difficult disk, or SSD. About of the time, there's no problem. Withal, you may encounter errors now and again, and ane of the most common is that your Mac is unable to write to the disk. Yous may see a message telling you that the drive is read-only. Fortunately, it'south not also difficult to fix the problem. In this commodity, we'll evidence you how.

What causes the "read-just" error?

There are ii possibilities when you see a message telling you a hard drive, USB stick, or other external storage media is read-simply.

  1. The drive is formatted in a fashion that means your Mac can read it but not write to it. This tin can happen with disks that are formatted every bit NTFS.
  2. Some permissions settings prevent your Mac or your user account from writing to the disk.

To determine which of these is causing the trouble, select the disk in the Finder and press Command-I, or right-click information technology and choose Become Info.

Under General, you lot should meet a list of parameters. Expect at the ane named Format. If information technology says NTFS, that's the trouble.

If the Format is APFS, macOS Extended, or FAT 32, then that is not the trouble, and you lot'll demand to bank check permissions.

  1. Look at the bottom of the Get Info window.
  2. Nether Sharing & Permissions, information technology will tell you what admission you have. If it says "read-but," y'all know the problem is permissions-related.

Tip:

CleanMyMac X's Maintenance module allows you to repair cleaved permissions on a disk with a couple of clicks. That might exist all you demand to practise to fix problems with only being able to read from external disks.

Repair disk permissions in Maintenance module CMMX

How to alter permissions on an external hard drive on your Mac

The post-obit applies whether the bulldoze in question is a hard drive, USB stick, SSD, or any other external media. There are several options, depending on what you identified as causing the problem.

How to fix hard drive read-merely issue

At that place are 2 options here. One is to reformat the drive to a format your Mac tin write to as well as read. This will wipe all the information from it, so you should make a backup or manually re-create of import files to another location start. Depending on how you format information technology, it may also cause problems if you lot demand to use the drive with a Windows PC. And so, only choose this option if yous know the drive volition only be used with Macs in the futurity.

The other selection is to use third-party driver software to enable your Mac to write to an NTFS-formatted deejay. At that place are a number of paid-for and some free options available.

How to reformat an external bulldoze:

  1. With the drive plugged into your Mac, go to Applications > Utilities and launch Disk Utility.
  2. Choose the external disk in the Disk Utility sidebar.
  3. Select the Erase tab.
  4. Blazon in a name for the reformatted drive.
  5. Select MacOS Extended (Journaled) from the dropdown menu.
  6. Press Erase.
  7. The drive will be wiped, reformatted, and when information technology's washed, your Mac will be able to write to it.

How to fix permissions problems

If the drive is correctly formatted for the Mac and you tin't write to information technology, the problem is likely to be related to permissions. Here's how to ready it.

  1. Select the drive in the Finder.
  2. Press Control-I to brandish the Get Info window.
  3. At the lesser of the window, click the arrow adjacent to Sharing & Permissions to brandish permissions.
  4. Click on the Privilege menu adjacent to your username and choose Read & Write.
  5. Close the Go Info window.

If your user account is non an admin user, y'all may have to use the padlock to unlock permissions settings and type in an admin username and countersign. You may also need to restart your Mac to become the alter to take effect.

In some circumstances, you may not exist able to change permissions in the Finder, or doing then may non fix the problem. If that happens to you lot, the next step is to use Disk Utility to fix the deejay.

  1. Become to Applications > Utilities and launch Disk Utility.
  2. Select the external deejay in the sidebar.
  3. Click on Starting time Assist.
  4. Printing Run to confirm that you lot want to try and repair the disk.

In versions of macOS upward to and including macOS 10.10 Yosemite, you could utilise Deejay Utility to repair permissions. The option appears in the Showtime Aid tab with two buttons, one to verify and 1 to repair permissions. If you are running a version of macOS where these options are bachelor, you should utilise them instead of the steps described above.

If y'all encounter an issue where a hard drive is read-but on your Mac, or perhaps a USB stick or flash bulldoze, information technology may exist that it is formatted as NTFS, which can be read past macOS but not written to. It may too exist a permissions event. If y'all follow the steps in this article, y'all'll be able to place which it is and prepare information technology quickly.