How to Delete Duplicate Files on External Hard Drive on Mac and PC

This article shows you how to find and delete duplicate files on external hard drive on Windows PC and Mac easily and quickly.

External hard drives are often used for backup purposes such as Time Machine backups. They can also be used to transfer files from one computer to another. During the process, many duplicate files may be created by mistake. By deleting duplicate files, you can free up a lot of storage space on your hard drive, increase its loading speed, and keep your files organized. In this article, I'll tell you 3 different ways to find and remove duplicate files from external hard drives.

 

Part 1. Find and delete duplicate files on external hard drive automatically

To find duplicate files on an external hard drive, the best way is to use Cisdem Duplicate Finder, a duplicate file finder app.

Why use Cisdem Duplicate Finder

This app can accurately and quickly identify all duplicate files on your external hard drives.

Key features:

• Scan one or multiple drives or folders: It works with external hard drives, internal hard drives, SD cards, and even cloud drives too.
• Find duplicate files across folders/drives: You can use it to easily find duplicate files across multiple external hard drives, or between your HDD and another drive such as computer's Internal hard drive.
• Find all types of duplicate files: Photos, videos, audio files, documents, etc.
• Detect similar photos: It also identifies similar photos, which is great for photographers and users who like to back up their photos to external hard drives.
• Smart auto-selection rules: If offers 8 selection rules to help you delete all duplicates with one click.
• Preview before deleting: You can preview detected duplicate files on external hard drive before deleting.
• Cross-platform: Available for Windows, Mac, Android, and iOS.

Delete duplicate files on external hard drive on Windows or Mac in 4 steps

Step 1. Add your external hard drive(s) to scan

Download and install Cisdem Duplicate Finder. Open it.

Free Download Windows 11/10/8/7 Free Download macOS 10.11 or later

Click the Add button to add your external hard drive. Click the Scan button, and this app will start finding duplicate files on this external hard drive.

• To find duplicate files on an external hard drive (or in a folder on it), add this drive (or folder) alone.
• To find duplicate files across multiple drives, external or internal, add these drives.

Step 2. View and preview duplicate files

When the app finishes finding, the results window will appear, displaying all the duplicate files found on your external hard drive under the All tab. You can also view different types of duplicate files (such as duplicate photos) under the corresponding tabs (such as the Image tab).

There are three view modes (Thumbnail, List and Info), allowing you to easily preview images, audios, videos and documents and view file information like name, size, location and resolutions. The preview feature can be especially useful when it comes to deleting duplicate photos on external hard drive. You can zoom in or out the preview for a better view.

The Images tab also displays similar photos (photos that look the same but are slightly different in resolutions, file sizes or formats) along with a similarity percentage for each.

Step 3. Select duplicates for removal

In each set of duplicate files, this duplicate file finder has automatically selected all but one file for deletion. You can also select/deselect by hand. In addition, there are selection rules to help you mass select.

Step 4. Delete duplicate file on external hard drive with 1 click

Once you are sure that all unwanted duplicates are selected. Click the Delete button in the bottom right corner. Click Yes in the message that appears to confirm the deletion.

The duplicates will be permanently removed from your external hard drive. If it were your computer’s internal hard drive instead of an external one, more removal options (such as Move to Recycle Bin/Trash) would be available.

Important: Please don’t eject your external hard drive that is connected to your computer while the scan or removal of duplicate files is going on.

Tip 1. How to scan duplicate files in external hard drive faster

It generally only takes seconds to compare thousands of files to identify duplicates. If there are a significantly large amount of files, the scan will take more time. Luckily, you are allowed to reduce the scan time by excluding files and folders from the scan.

Before you click the Scan button in step 1, click the settings icon in the top right corner. In the settings window that appears, you can exclude items.

• Exclude folders. In the Ignore folders and files in the list section, add the folder(s) of your choice for exclusion. For example, you can exclude a folder that you are sure doesn’t contain duplicate files.
• Exclude file types. In the Ignore files of particular extensions section, enter file extensions of your choice. For example, if you enter MP3, it will skip all the MP3 files when scanning your external HD for duplicates.
• Exclude files by size. You can set the minimum and maximum file size. For example, if you aim to find and remove large duplicate files on your external hard disk quickly, set the scan to skip all small- and medium-sized files.

Tip 2. How to scan similar photos on your external hard drive?

Strictly, there are two types of duplicate photos: the ones that are exactly the same regardless of name, and the ones that look identical but are actually slightly different. This tool can find both. You can go to the Settings window to turn on/off the similar image detection as your need. Once turn it on, you can customize the level of similarity it searches for duplicates. If you turn this feature off, the app will take less time to find all exact duplicate files on your external hard drive.

 

Part 2. Manually find and delete duplicate files on your external hard drive

If there aren’t many files on your external hard drive, you can try getting rid of duplicate files on it manually by using the built-in file manager on your computer - File Explorer for Windows or Finder for Mac.

Why use the built-in file managers

There are some advantages to find duplicate files on your external hard drive using these 2 built-in file managers:

• No software installation required: Both these 2 file managers are already built into your computer. So you don’t need to install any third-party software.
• Completely free: They are free to use.
• Full control: It requires you to compare file names, sizes, and other detailed information one by one. Then you can manually select duplicates to remove. This may be a bit time-consuming, but you are in full control of the whole process.

Use Windows File Explorer

Applies to: Windows computers

Follow the steps below to delete duplicate photos on external hard drive with File Explorer, which can also help you deal with other types of duplicate files.

Step 1. Connect your external hard drive to your PC.

Plug the external hard drive's USB cable into your computer's USB port.

Step 2. Navigate to your external hard drive in File Explorer.

Press Win + E on the keyboard. Or click the folder icon on the taskbar. Find your external hard drive on the left menu. Open it.

Step 3. Filter files in external hard drive by type.

To filter specific file types such as images, type kind:=picture in the search bar at the top-right corner. Then it’ll sort out all the images in your external hard drive.

Step 4. Sort files in external hard drive by name/size.

Click on View > Details. Click on Sort > Group by > Name/Size. Now you can quickly find files that have the same file name or file size, which are usually duplicate files.

Step 5. Manually check and delete duplicate photos

Go through the photos displayed in the File Explorer window. Find the duplicates by comparing their content, name, size, etc. Right-click the duplicate files you have found and select Delete to move them to the Recycle Bin.

 

Use Mac Finder

Applies to: Mac computers

Finder is a file manager included in macOS. Below is how to use it to get the job done.

Step 1. Connect your external hard drive to your Mac.

Use a compatible cable to connect the external hard drive to your Mac. Open Finder. In the left sidebar of Finder, you’ll see this drive appears.

Step 2. Navigate to your external hard drive in Finder.

Click the name of your external hard drive in the left sidebar to enter it.

Step 3. Filter files in external hard drive by type.

Press Command + F to bring up the advanced search in Finder.

In the first drop down menu, choose Kind. Then choose a file type in the next drop down menu, like Image, Document, or Music. You can also further choose a specific file format if needed.

Now the Finder window displays all the files of your chosen kind on your external hard drive.

Step 4. Sort files in external hard drive by name/size.

Choose the sort order that makes it easy for you to compare files to identify duplicate files, such as Name or Size.

Step 5. Manually find and delete duplicate files.

The Preview pane on the right of Finder can greatly help you compare files. In each set of duplicate files that you’ve found, delete the unwanted one(s) by dragging them to Trash. Or right-click and select Move to Trash.

Tip. You can also identify duplicate files on external hard drive on your Mac with Terminal, an app included in macOS. But note that this method is not that user-friendly. Also, this method only identifies duplicates. You still need to delete duplicates manually. Here’re the details of this method.

 

Part 3. Automatic vs manual Methods: Which one should you choose?

If you’re not sure whether you should go with the automatic method (in part 1) or manual methods (in part 2) in this article, here’s a quick comparison to help you decide:

 

Q&As

Why are there duplicate files on your external hard drive?

There could be various reasons. Here’re some possible ones.

• When you backed up files using your external hard drive, duplicate files already existed in the files you backed up.
• Or, you, most likely unintentionally, used it to back up the same files twice or more.
• When you organized files on your drive, you moved files by copying and pasting instead of using drag and drop.

Knowing the reasons may help prevent duplicates from occurring in the first place.

How do you avoid duplicate files on an external hard drive?

These are 5 suggestions may help you prevent duplicate files on external hard drive:

• Avoid unnecessary backups.
• Delete files on your external hard drive after you transfer them to your Mac or PC, if you think that it’s unnecessary to keep them there anymore.
• Use duplicate file finder software on a regular basis.
• Name your files in a logical way, which may help you quickly and easily identify duplicates.
• Use drag and drop instead of copy and paste when you move files to a folder.

 

Conclusion

Duplicate files can waste space on external storage devices. Getting rid of useless duplicate files on your external hard drive can free up storage space and make room for new files or backups. In addition, deleting duplicates can make it easier when you want to find certain files. This article talks about how to identify and delete duplicate files on external hard drive on Windows PC or Mac efficiently. I hope it’s helpful.