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

Rosa Reyes
June 04, 2023 Preview 41.8K Preview 6
share it facebook share it Twitter

This article will show you how to find and delete duplicate files on external hard drive on Mac and Windows PC 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 computer to computer. Duplicate files may slowly accumulate over time as you use your external hard drive. To make effective use of the storage space on your drive, it’s a good idea to find the duplicate files on it and get them deleted. The article will show easy ways to remove duplicate files from external hard drive.


Part 1. Find and delete duplicate files on external hard drive on Mac and PC in 1 minute or less

To find duplicate files on an external hard drive, the best way is to use Cisdem Duplicate Finder, a duplicate file finder app. This app can accurately and quickly identify duplicate files (exactly identical files regardless of name) on your computer’s internal hard drive, external storage devices, and even cloud storage services and allows you to easily and quickly to remove unwanted duplicates.

In addition to duplicate images, the app can find non-exact duplicates (photos that look the same but are different in resolutions, file sizes or formats) and similar photos.

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

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

Download and install Cisdem Duplicate Finder. Open it.

Free Download   Free Download

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

add drives to scan

  • To find duplicate files on a drive (or in a folder on it), external or internal, add this drive (or folder) alone.
  • To find duplicate files between two drives, external or internal, add both drives.
  • 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 different tabs (such as Image).

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 also zoom in or out for a better view.

The Similar Image tab displays non-exact duplicates and similar photos.

view and preview duplicate files

view similar images

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 selection rules icon to help you mass select.

a list of the eight selection rules

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 OK in the message that appears to confirm the deletion.

delete duplicate files on external hard drive on mac

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 Trash/Recycle Bin) would be available.

Note: Don’t eject your external hard drive while the scan or removal is going on.

Tip: How to reduce time to scan external hard drive for duplicate files

With advanced algorithms, this Cisdem external hard drive duplicate file finder scans for duplicates by comparing file hashes or doing byte-by-byte comparison. It generally only takes seconds to scan thousands of files. For a significantly large amount of files, it will take more time.

Here’s the good news! You can exclude files and folders from the scan so as to lessen the time it will take.

  • Exclude folders Before you click the Scan button, click the Settings icon in the top right corner. Go to the General tab. In the Ignore folders and files in the list section, click the Add button to add specific folders and files for exclusion.
  • Exclude file types In the Ignore files of particular extensions section. Click the Add icon to enter file extensions. 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 get rid of large duplicate files and quickly free up space on your external hard disk, then you can set the scan to skip all small- and medium-sized files.

exclude folders and files

In addition, there are other settings settings icon. By customizing them based on your needs, you will be rewarded with a more efficient duplicate removal.

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

There are three ways to get the job done by hand.

Use Finder

Applies to: Mac computers

How to delete duplicate files on external hard drive mac such as photos that are stored on them? I have over 15,000 duplicate photos on my Photos, half of it stored on the external HD. I tried to find these duplicates manually, but it was a waste of time and energy. Is there a duplicate file finder what could help me to find and remove these duplicate photos on Mac? Any help will be greatly appreciated. - Asked by a Mac user

How do Mac users find and delete duplicate files on external hard drive? The best way is to use a duplicate file finder for Mac. You can also do it by hand. It’s not as hard as it seems. However, it can be a waste of time and energy if there are a lot of duplicate files on your external hard drive. Anyway, here’s how.

Step 1. Plug your external hard drive into Mac. Go to Finder. In the Devices sidebar, select the external drive.

Step 2. Use shortcut Command-F. A search bar will appear.

Step 3. Select Kind among the available search parameters. Select the file kind of your choice in the second dropdown list. Also choose a specific file format if needed.

manually find duplicate files on external hard drive with Finder on Mac

Step 4. Sort the listed files by name or other parameters, preview and compare, and find the duplicate files. You can move the unwanted ones to Trash.

Use Terminal

Applies to: Mac computers

You can also identify duplicate files on external hard drive or Mac’s internal hard drive with Terminal. Note that it only identify duplicates. You still need to delete the files manually. Terminal comes with every Mac.

Step 1. Go to Finder > Applications > Utility. Find and open Terminal.

Step 2. If you want to find the duplicate files in a folder, say Downloads, you can use the cd command by typing cd ~/Downloads and press the return key.

Step 3. Enter the command: find . -size 20 \! -type d -exec cksum {} \; | sort | tee /tmp/f.tmp | cut -f 1,2 -d ' ' | uniq -d | grep -hif – /tmp/f.tmp > duplicates.txt. Press return.

Step 4. Open the file duplicates.txt and you will find a list of duplicate files. Now you can manually find and delete them.

Use File Explorer

Applies to: Windows computers

Your computer comes with File Explorer, a file manager app. You can use it to locate the files you need quickly and easily. Here you can know how to delete duplicate photos on external hard drive via File Explorer:

Step 1. Connect your external drive to your PC.

Step 2. Press “Win” + “E” File to open File Explorer. Navigate to your external hard drive.

Step 3. Click on View > Details.

Step 4. Click on Sort > Group by > Size.

sort files

Step 5. Type in the extension such as .jpeg in the upper-right search box.

Step 6. Go through your files and identify the duplicates.

Step 7. Delete the duplicate files you have found.

Bonus tips

Why there are so many duplicates on external hard drives?

It’s not uncommon to have duplicate files on your computer and external hard drives. As a matter of fact, duplicate files are almost inevitable.

They can be there due to multiple imports of the same files, multiple copies of backup, app (such as iTunes) bugs, etc. They can occur when you unknowingly transfer files to your external hard disk where the same files already exist.

Another cause is file compression. Sometimes we compress photos to make them smaller in size for emailing or uploading. In a case like this, there can be duplicate copies of the same photos. They are identical in content but different in size.

Whatever the cause is, it’s important to clean them up. By doing so, you can free up storage space and keep your files more organized. It will also help if you know how to prevent them from occurring.

How to avoid duplicate files on 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.

In conclusion

Above are the common ways on how to find duplicate files on external hard drive on Mac or Windows PC. Duplicate files can waste space your internal and external hard drives. By getting rid of useless duplicate files with the help of software like Cisdem Duplicate Finder, you can free up storage space on your external hard disk. Do you think this guide on how to identify and remove duplicate files helpful? Leave a comment and share your thoughts and opinions.

Rosa Reyes
share it facebook share it Twitter

Rosa has worked in Mac software industry for more than eight years. She believes that the purpose of software is to make life better and work more productively. In addition to writing, Rosa is also an avid runner.

share it facebook share it Twitter
Comments (6) Leave a Reply

Name *

Comment *

  • Kerstin Olesch

    Thank you so much. The duplicate file finder tool you recommended is easy and quick to use. Saved me a ton of time and space on my hard drive!

    0 months ago Reply

    Name *

    Comment *

  • Limnos

    I have a lot duplicate picture and movie files on my MacBook, this duplicate file finder app helped me free up 53GB space. I can't express my gratitude in words.

    7 years ago Reply

    Name *

    Comment *

  • Melissa

    I want to delete duplicate files from other storage device, not only from Mac or external hard drives, can Cisdem duplicate file finder help me do that?

    7 years ago Reply

    Name *

    Comment *

    • Rosa Reyes

      Hi, Melissa, Cisdem DuplicateFinder fully supports deleting duplicate files from Mac HDD, SSD, external hard drives, cameras, iPods, USB flash drives, memory cards, etc.

      7 years ago
  • Lareina

    My hard drive seems to create "duplicates" of all my files. I don't want to check it one by one. Cisdem DuplicateFinder did a great job with works very well and remove duplicate files from my external hard drive quickly.

    7 years ago Reply

    Name *

    Comment *

  • Phoebe

    My mac was running out of space, and i transferred many files to external hard drive. I found many duplicate photos and music and tried to delete them manually. Oh, my god, I even didn't know there is such a nice tool like Cisdem DuplicateFinder that can help me remove them.

    8 years ago Reply

    Name *

    Comment *

Hot Articles

How to Clean Up Mac including New iMac How to Find and Delete Duplicate Files on Mac: 4 Proven Ways How to Delete Unwanted Files Easily on Mac and Windows
Home > How to Delete Duplicate Files on External Hard Drive on Mac and PC