How to Defragment External Hard Disk in Windows 10

Learn how to defragment external hard disk with Windows tool and with an external hard drive defrag software.


By Lucas / Updated on May 12, 2023

Share this: instagram reddit

Should I defrag the external hard drive?

Should I defragment my external hard drive? May that hurt my external hard drive? In this part, we’ll explain how HDD works, where fragments come from, and how defragmentation performs to improve the hard drive performance. After a brief reading about the working details of your external HDD, you can select the appropriate solution according to your situation.

1. About HDD

HDD Head

When the HDD is used for a long time, the files will be scattered to discontinuous positions in the disk. If a program wants to read the files again, the relevant component must go to a different storage place to read, which is why your computer gets slower than before.

2. About fragment


There are 3 common sources of fragments.

• Temporary swap files
Generally, the OS will generate temporary swap files on the hard disk. The hard disk space will be occupied by these files that have been virtualized into memory. The virtual memory management program frequently reads and writes on the hard disk, which can result in a lot of fragments.

• Download large programs.
The large files you downloaded will be divided into several small files and stored on the hard disk.

• Frequently delete files.
The more frequent the file deletion, the more fragments.

3. About defragment

The disk defragmentation is a specific solution to these scattered files.

By using Windows tool or professional hard drive or external hard drive defrag software, the process of rearranging the fragments of the disk, thereby increasing the operating speed of the computer.

4. About external hard drive

USB interface

Though the theoretical maximum transmission speed of USB 3.0 is 5Gbps (about 625MB/s), nearly 10 times faster than USB2.0. If you want to use an external hard drive with a 3.0 interface as a work drive not a backup drive to store files, you still need to keep it in nice maintains.

Guide--How to defragment external hard disk

Normally, there are 3 ways to defragment your hard disk. This part will show you how to use the “Defragment and Optimize Drives” app and CMD from Windows itself to defragment your external hard disk and recommend you an external hard drive defrag software to defragment drives with a better experience.

1. Use Defragment and Optimize Drives to defrag

First, you need to connect your external hard disk to your computer and ensure it plug steadily.

Step 1. Please type “Defrag” in the search box. And click the best match “Defragment and Optimize Drives” to open it.

Optimize Drive Tool

Step 2. Then the “Optimize Drives” window will appear. In the Status box, you can see all readable drives that are allowed to optimize and defragment.

Optimize Drive

Step 3. Select the drive you want to defragment. You can choose according to the “Current status” column.

Defragment in WIndows 10

Step 4. Click “Optimize” to defragment the selected drive. You need to wait for a while.


2. Defrag via CMD

Step 1. Press “Windows” + “R” to open the “Run” box, then type “cmd” to open CMD.

Step 2. Insert “defrag x:” (x is the name letter of your external hard drive.) and hit “Enter”.

Then you can wait for the procedure.

Defrag via CMD

3. An external hard drive defrag software

If you have tried “Defragment and Optimize Drives”, you may find that you cannot run the operation on multiple drives at the same time. And if you insert the wrong order in CMD, your hard drive will be damaged. Thus, we recommend powerful defrag software to help you defragment your hard drive securely and quickly.

AOMEI Partition Assistant Professional is a pragmatic disk manager for Windows 10/8/7/XP/Vista users. Its “Disk Defrag” feature can handle multiple drives at the same time. And this function can automatically analyze the whole hard drive, you can select to execute the defragmentation or not according to the analysis.

Download ProDemo Win 10/8.1/8/7/XP
Secure Download

Note: If the partitions on your external hard drive are not NTFS partitions, please convert them to NTFS partitions before we start to defragment.

Step 1. Install and launch AOMEI Partition Assistant, right-click on the disk and select the "Disk Defrag" function.

Disk defragment

Step 2. Check the partition needed to be analyzed, and click "Analyze". You need to check the partition, not select it. This function currently only supports NTFS partitions, so it will only list NTFS partitions on SSD, HDD, and USB drives.


Tip: You can click "Pause" to halt the process and resume later, or click "Stop" to end the analysis process completely.

Stop and Pause the defrag

Step 3: The program will score the partition based on the fragmentation rate when the analysis is over.

There are 3 statuses according to the score:

Normal: Score≥90. The partition is in good condition, with no need for defragmentation.
Suggest defragmenting: 60≤Score<90. The current partition has some fragments, which suggest running defragmentation.
Defragment now: Score<60. There are many fragments in the current partition, suggest running the defragmentation immediately.

You can check the distribution of fragments through the Tetris view.

Step 4. After the analysis is finished, you can click on "Details" to see more information about the analysis results:

•Total files and directories
•Fragmented files
•Fragmentation Rate


Step 5. Click the "Defrag" button to start the defragmentation.


Tip: You could click "Pause" to halt the procedure and resume later, or click "Stop" to terminate the process completely.

After the defragmentation is completed, the partition will be scored according to the defragmentation result.


Note: If the fragment files are in use, they cannot be defragmented.

Defragmentation is like rearranging the chaotic fragmented files in the hard disk. After rearranging orderly, you can free up more running space for the hard disk. When it’s finished, the operating speed of the computer will be greatly improved, which is also helpful for the maintenance of the computer. Therefore, if you need, you can set a schedule defrag to keep the health of your disks.

How to defragment external hard disk? AOMEI Partition Assistant provides you with a perfect answer. This software has various convenient functions to help you manage all your disks, its “App Mover” function can transfer large programs and your games between HDD and SSD without any worry of reinstallation to release more free space on your disks. What’s more, the “Migrate OS to SSD” function can help you move OS from one disk to another with no need of reinstalling, you can boot successfully after you set the boot order in BIOS.

Lucas · Staff Editor
I prefer peaceful and quiet life during vacation,but sometimes I watch football match if my favorite club performs brilliantly in that season. And I love reading, painting and calligraphy, thus I send my friends festival handwriting cards every year.