Why Your Mac Says 'Disk in Use' When Nothing's Open

You’ve closed everything. Safari, gone. Finder windows, closed. That document you were editing, saved and quit. You click eject on your external drive and macOS tells you something is still using it.

You check again. Nothing visible is running. No progress bars anywhere. The drive is just sitting there, doing nothing as far as you can tell. But something, invisible to you, has its hooks in your disk.

This is one of the most frustrating experiences on macOS because the problem feels impossible. You did everything right. You closed your work. And the system is still blocking you for reasons it won’t explain.

The invisible processes

Most of what runs on your Mac is invisible. Behind the apps you interact with, dozens of background processes handle tasks you never think about: indexing files for search, generating thumbnails, syncing data, monitoring for changes.

These processes don’t have windows. They don’t appear in your Dock. Some of them don’t even show up in Activity Monitor unless you know where to look. But they can all access your external drive, and any one of them can prevent ejection.

When macOS says “one or more programs may be using” your disk, it’s usually not lying. Something is using it. The unhelpful part is that macOS refuses to tell you what.

The usual suspects

Spotlight is the most common invisible blocker. The moment you connect an external drive, Spotlight starts indexing it. The indexing processes (mds, mds_stores, mdworker) run in the background with no visible indication that they’re working. They can hold files open for minutes or hours depending on how much content is on the drive.

QuickLook is sneakier. When you browse a folder, macOS generates thumbnails and previews. The QuickLook processes (QuickLookUIService, quicklookd) sometimes hold onto file handles even after you’ve closed the Finder window. You looked at the folder ten minutes ago, but QuickLook is still thinking about it.

Time Machine, if enabled, constantly monitors backup drives. Even when no backup is running, the backupd process maintains connections to Time Machine volumes. It’s watching for changes, ready to start the next backup.

iCloud and other sync services can access external drives if you’ve stored synced folders there. The sync daemon might be checking file status or waiting to upload changes.

Finder itself runs background operations you don’t see. File metadata updates, trash management, and sidebar calculations all happen invisibly. Closing a Finder window doesn’t necessarily end Finder’s relationship with a drive.

Finding the culprit

The only reliable way to see what’s blocking your drive is Terminal. Run this command, replacing the drive name with yours:

lsof /Volumes/YourDriveName

This lists every process with open files on the drive. The output is technical but readable. The COMMAND column shows process names, and the NAME column shows which files they have open.

Common things you’ll see:

• mds or mdworker: Spotlight indexing
• QuickLookUIService: Thumbnail generation
• Finder: A Finder operation or sidebar reference
• backupd: Time Machine monitoring
• bird or cloudd: iCloud sync

If the list is long, you’ve found your invisible users. If it’s empty, the problem might have resolved itself, and you can try ejecting again.

Stopping the invisible processes

Once you know what’s blocking the drive, you have options.

For Spotlight, disable indexing on the drive:

sudo mdutil -i off /Volumes/YourDriveName

This tells Spotlight to leave the drive alone. You can re-enable indexing later if you want to search the drive’s contents.

For QuickLook, reset its cache:

qlmanage -r cache

This clears whatever QuickLook was holding onto and usually frees the drive.

For Finder, restart it by holding Option, right-clicking the Finder icon in your Dock, and selecting Relaunch. This resets all of Finder’s connections.

For other processes, you can quit them from Activity Monitor. Search for the process name, select it, and click the X button. Most system processes restart automatically, but the drive should be released.

Preventing the problem

If you don’t need to search an external drive with Spotlight, add it to the Privacy list in System Settings under Siri & Spotlight. Drives on this list are never indexed, which eliminates the most common ejection blocker.

Create a file called .metadata_never_index in the root of your external drive. Spotlight checks for this file and skips indexing any drive that has it. This is useful for drives you move between multiple Macs.

Be aware of what’s stored on your external drives. If you put iCloud folders, sync folders, or Time Machine backups there, expect background processes to access them constantly.

The better approach

Hunting through Terminal output every time you want to unplug a drive gets old fast. The information is there, but the workflow is clunky.

Ejecta shows you the same information in a cleaner format. Click on a blocked drive, see what’s blocking it, close that process with another click. No commands to remember, no output to parse.

The underlying problem is that macOS runs dozens of invisible processes that can grab your drive. Knowing they exist is the first step. Being able to see exactly which one is the problem, without switching to Terminal, is a much better experience.