How to fix
Windows ejecting USB mass storage device errors
on Windows

Windows says the USB mass storage device is in use, and it will not eject even after you close the drive window.

The message usually appears when you try to use Safely Remove Hardware or another eject option and Windows still sees an open handle on the drive. The visible symptom is simple but disruptive: the removal attempt fails, the system warns that a file or program is still using the device, and the drive stays mounted even when you expected it to be ready for unplugging. This can happen with USB flash drives, portable SSDs, and external hard drives, and it tends to show up at the moment a user finishes copying, moving, or opening files from the device.

The failure is not always tied to a damaged drive. In many cases, Windows is blocking removal because a process still has an active read or write request, even if the user no longer sees an open file window. File Explorer previews, thumbnail generation, search indexing, antivirus scans, cloud sync clients, backup tools, and background cache updates can all keep a volume marked as busy for longer than expected. When that lock remains in place, the system refuses to release the device because unmounting too early could interrupt file writes and leave data incomplete.

A second path to the same message involves the driver layer. USB mass storage devices depend on a chain of storage, controller, and policy drivers that tell Windows how the disk should be handled, when caching is allowed, and how the device should be detached. If one of those drivers is outdated, unstable, or responding slowly, Windows may not complete the handoff needed for a clean eject. The result looks identical to a simple file-in-use problem, even though the real fault sits lower in the storage stack.

That distinction matters because removable storage is managed differently depending on the device policy in use. Windows can operate a drive in a mode that favors write caching and performance, or in a mode that favors immediate removal with less caching. When the system is set to a more cautious policy, or when a device has just finished a write operation, it expects a clean flush before detaching the media. A USB drive is therefore not just a physical object in this scenario, but a live storage endpoint that Windows is still coordinating with in the background.

The user-facing warning comes from that coordination process. Windows must make sure file system metadata, directory entries, and pending write operations are finished before it drops the volume. If the operating system cannot prove that the device is idle, it protects the data by refusing the eject request. That protective behavior is useful, but it becomes frustrating when the system keeps a device busy long after the user has finished working with it.

Some cases are triggered by a background application that never fully released the drive. A document editor may keep a recent file open, a media player may still be reading a clip, or Windows Search may still be cataloging the contents of the removable disk. Even a simple thumbnail cache can leave the device in a state where Windows believes it is still active. The message then appears because the system is not responding to the act of unplugging itself, but to the active reference that remains attached to the volume.

Another common cause is a stale shell reference. File Explorer can keep the drive busy if a folder view is open, if a preview pane is inspecting files, or if the system has not fully cleared the last directory session. In those cases, the drive may look idle on screen, yet Windows still has one or more handles open internally. The eject operation fails because the shell has not finished releasing the device, and the operating system treats that as a sign that data could still be changing.

Driver failures create a different mechanism. The USB mass storage class driver and the controller driver must agree on when the device can be detached. If the driver stack does not respond properly, Windows may never receive the confirmation it needs to finish the removal sequence. A driver error can also make the device appear more active than it really is, which causes the operating system to hold the eject request until the timeout logic intervenes.

Device policy can complicate the problem further. Some systems and some drives operate with cache settings that are designed to improve throughput, especially during large transfers. That improves speed, but it also means Windows has to finish flushing pending writes before the volume is safe to remove. If the user tries to eject immediately after a copy operation or after a file was only recently closed, the operating system may still be working through those cached instructions and will reject the removal request until the flush is complete.

The message is therefore a sign that Windows is enforcing a storage safety rule, not a random refusal. The operating system is trying to guard against corruption by making sure the file system is stable before the hardware disappears. That rule is especially relevant on portable storage because users often disconnect those devices suddenly, and a single interrupted write can damage the file table or leave recently changed content unusable.

USB mass storage also sits at the boundary between hardware and software. The drive enclosure, the USB cable, the controller, the Windows driver, and the open processes all have to behave correctly for removal to succeed. When one layer is slow or stale, the others have to wait. That is why the same warning can appear even when the drive itself is healthy and the real issue is only a lingering lock or a driver that has not refreshed properly.

Windows 10 version 1809 introduced a more forgiving removal policy for new drives through the default quick removal setting, which reduces the need to rely on manual ejection in some cases. Even so, users still run into the eject warning when a process remains attached or when the driver stack is not cooperating. The problem is therefore a mix of file access state, storage policy, and driver behavior, and each one points to a different repair path.

Here are 6 solutions to fix Windows ejecting USB mass storage device errors.

Fix 1. Close open files and background apps

Releasing every active file handle is the fastest way to clear a simple in-use lock.

Close any document, photo, or media file opened from the USB drive.

Exit the program that last accessed the drive.

Check File Explorer windows that show the USB contents.

Close any preview pane or thumbnail-heavy folder view.

Try ejecting the USB device again.

Fix 2. Restart the computer

A restart clears stale handles and resets simple storage activity that can survive a normal app close.

Save your work and close open programs.

Disconnect any other unnecessary external devices.

Select Start, then choose Power.

Click Restart.

After Windows loads, reconnect the USB drive and try ejecting it again.

Fix 3. Run the Hardware and Devices troubleshooter

The built-in troubleshooter can correct minor hardware and driver faults that keep the device from releasing properly.

Right-click the Windows key and choose Settings.

Open Update and Security.

Select Troubleshoot.

Choose Hardware and Devices.

Click Run the troubleshooter.

Apply any fix Windows recommends and restart the computer if prompted.

Fix 4. End tasks in Task Manager

Stopping the process that still holds the drive open removes the lock without waiting for the application to release it on its own.

Right-click the Windows key and choose Task Manager.

Look for apps that may still be using the drive.

Select the process you want to stop.

Click End task.

Repeat for any other related processes.

Try ejecting the USB device again.

Fix 5. Change the drive policy in Device Manager

Switching the device to a removal-friendly policy can reduce write caching delays that keep Windows from finishing the eject sequence.

Right-click the Windows key and open Device Manager.

Expand Disk drives.

Right-click the USB mass storage device and open its properties.

Find the removal policy or performance setting.

Select Quick removal if it is available.

Restart the computer if Windows asks for it.

Try removing the drive again.

Fix 6. Update USB drivers

Refreshing the USB driver stack helps when the eject failure comes from a controller or storage driver that is not responding cleanly.

Right-click the Windows key and choose Device Manager.

Expand Universal Serial Bus controllers.

Right-click the USB device or controller entry.

Select Update driver.

Choose Search automatically for updated driver software.

Let Windows install any available update.

Restart the computer and test the eject again.

Šaltinis: easeus.com