Why is my hard drive read only?

A drive that opens but refuses to save anything is usually not broken. The common causes are an NTFS drive on a Mac, a permissions setting, write protection on the device itself, or a file system error the computer will not build on. This page explains how to tell them apart and how to fix each one without losing data.

Written by Essential Data RecoveryPublished 2026-09-13Owner-reviewedRevision 1

A closed portable hard drive resting under a smooth grey pebble on pale oak wood so it cannot move, in warm morning light

Your drive opens. You can see the files and copy them off, but the moment you try to save, move or delete anything, the computer refuses. That is a read-only drive, and it is usually not a broken drive. Behind nearly every case is one of five things: an NTFS drive attached to a Mac, a permissions or ownership setting, write protection on the device itself, a file system error the computer will not build on, or the stricter format rules on iPhones and iPads. This page goes through them in order, then covers the safe route to a writable drive, which always starts with copying your data off first.

Cause 1: it is an NTFS drive and you are on a Mac

The most common version of this problem has a simple shape: the drive was formatted on a Windows PC, and the computer refusing to write is a Mac. macOS can read NTFS, the format Windows uses by default, but it cannot write to it. Paragon Software, which sells one of the drivers that add that ability, describes the symptom exactly: you can read the data on an NTFS drive from a Mac, but you cannot write, copy, edit or delete anything on it. Nothing has gone wrong with the drive. It is carrying a file system the Mac does not write, so the Mac treats the whole volume as read-only.^[1]

The fix is to copy the data off and reformat into a format both platforms can write. Apple's Disk Utility guide names MS-DOS (FAT) and ExFAT as the file systems compatible with Windows, and points Mac users to ExFAT for Windows volumes over 32GB. For a drive that will only ever meet Macs, APFS is the default on macOS 10.13 or later. The trade-offs between the formats are in the NTFS vs exFAT article linked below.^[2]

Cause 2: permissions and ownership

If the drive is the right format for the computer, check who is allowed to write to it. On a Mac, Finder's Get Info window has a Sharing & Permissions section that assigns each user a privilege: Read only lets a user open the item but not change its contents, while Read & Write lets them change it. A disk set to Read only for your account looks exactly like a read-only drive. Drives that have moved between Macs can carry settings from the previous account, which is why Apple documents how to change an item's owner in that same window.^[3]

Windows has the equivalent at file level: the read-only file attribute on files and folders, set or cleared with the attrib command (attrib +r sets it, attrib -r clears it). This cause shows itself as one file or folder refusing changes while the rest of the drive writes normally.^[4]

Cause 3: the device itself is write-protected

Some drives and memory cards carry protection at the device level rather than the file level. The oldest form is physical: a small lock switch the computer obeys by refusing writes. There is also software write protection. Windows can mark an entire volume read-only, and DiskPart's attributes volume command sets or clears that attribute, with "attributes volume clear readonly" removing it from the selected volume. If the whole drive refuses writes on Windows, this is the check to run, and the write-protected drive guide linked below walks through the switch, the attribute and the rest.^[5]

Cause 4: the file system is in an error state

The fourth cause is the one to take seriously. When a computer finds a file system in an inconsistent state, it can refuse to write to it until the damage is dealt with. Linux documents this behavior explicitly for its ext4 file system: with the errors=remount-ro option, the kernel remounts the whole filesystem read-only the moment it detects an error. The drive has not stopped working; it has been quarantined until it is repaired.^[6]

Windows arrives at the same situation by another road. It sets a dirty bit on a volume whose file system may be inconsistent, whether because changes were outstanding or the machine shut down before they were committed. When that bit is set, the volume is checked automatically at the next restart and chkdsk runs to verify the file system and attempt repairs. Microsoft's documentation does not describe Windows mounting a dirty volume read-only, so on Windows a damaged file system more often announces itself as errors, missing folders or a drive that will not open at all.^[7]

A drive that wrote normally yesterday and refuses writes today has changed, and the change deserves respect before it gets a repair. Copy what matters off the drive first. Repair tools can finish what an error started, and a read-only state that arrives alongside slow file listings, a volume that disappears, or a drive that takes minutes to open may be a failing drive rather than a confused file system.^[7][6]

iPhones and iPads

Plugging the drive into a phone changes the rules. Apple says an external storage device used with iPhone must have a single data partition and be formatted as APFS, APFS (encrypted), macOS Extended (HFS+), exFAT (FAT64), FAT32 or FAT, and the iPad page carries the same note. NTFS is not on that list, which is why a drive that works on a Windows PC misbehaves on a phone. The read-only experience is not a blanket rule of iPhones, though. Apple's own guide has you copy files to a supported storage device from the Files app, rename or erase the connected drive, and reformat an external drive to APFS, ExFAT or MS-DOS (FAT) on the device. On a supported format, an iPhone or iPad writes. Importing a camera card into the Photos app is a separate path again.^[8][9]

The fix: move the data, then reformat

Reformatting deletes everything on the drive. Apple states it plainly: erasing a storage device deletes everything on it, and if you have any files you want to save, copy them to another storage device before erasing. A read-only drive can still be read in almost all of the causes above, which makes this the easy case. Get the data off first, then change the drive.^[10]

Which format to pick follows from where the drive will be used. A drive that only meets Macs suits APFS, the default on macOS 10.13 or later. A drive shared between Macs and Windows PCs suits ExFAT, Apple's suggested Windows-compatible format for volumes over 32GB. If the read-only state turns out to be permissions rather than format, no reformat is needed at all: fixing the privilege in Get Info, or clearing the read-only attribute on Windows, leaves every file where it was.^[2]