How to Find and Delete Duplicate Files on External Hard Drive on Mac: 3 Ways

2019-04-10 21:52:25 / Posted by Rosa Reyes to Utility Follow @ Rosa

What is the best way for Mac users to find duplicate files on external hard drive and get them deleted all at once? You can find the answer here.

As time goes, you will have more and more files on your Mac. The older your Mac is, the more likely your hard drive is running out of space. To free up space on Mac, one solution is to get rid of unwanted files such as duplicate files. Another solution is to transfer part of your files to an external hard drive. However, when you transfer files back and forth between your Mac and external hard drive, duplicate files may end up on both.

Best way to find and delete duplicate files on external hard drive on Mac

You can use Cisdem Duplicate Finder for Mac to effectively identify and delete duplicate files on Mac’s internal hard drive or SSD, external hard drive, memory card, USB flash drive and other external storage devices.

It can find and remove duplicate photos, audios, videos, documents and other types of duplicate files by content or by filename (depending on settings).

pie chart overview of duplicate files

Find and delete duplicate files in 3 easy steps

Here’s a basic guide to duplicate files removal. This guide is applicable to external hard drive, Mac’s internal storage, memory card, etc.

Step 1Add your external hard drive to scan

Download and install Cisdem Duplicate Finder for Mac. Launch it. Connect your external hard drive to Mac. Drag the hard drive into the duplicate file finder. You can customize settings if needed. Click Scan.

add a external hard drive to scan for duplicate files

Step 2Preview duplicate files

Once the scan is finished, you can click Overview to find a pie chart overview of duplicate files. Duplicate files will be grouped by file type (Documents, Images, Music, etc.). You can sort them by name, size, etc. and search by keyword.

The preview feature is powerful, allowing you to preview photos, videos, audios, documents and spreadsheets directly in the app. You can change the preview mode by clicking the icons in the upper right corner of the preview window.

preview duplicate files

Step 3Delete duplicate files

The duplicate file finder will auto-select duplicates for you to delete. You only need to click the Delete button to eliminate duplicate files on your external hard drive and other added drives or folders.

By clicking the menu icon in the upper left corner of the preview window, you can choose from the four selection options (Select Oldest, etc.) provided. You can also select manually.

Note that the selected files on the external hard drive will be permanently deleted if you click Delete. For duplicates on Mac’s internal hard drive, there are three removal options.

remove duplicate files from external hard disk permanently

Tip: You can stop the scan process at any time, and real-time scan result will be provided. Don’t eject your external hard drive while the scan goes on.

A more advanced guide

As one of the best duplicate file finders for Mac, Cisdem Duplicate Finder allows high degree of customization and provides an array of filters and options.

Before scanning, you can set the scan and removal settings. Click the gear icon in the upper right corner of the interface. Under General, you can change Scan Method and Removal Method. Move to Trash is the default way to remove selected duplicates and allows easy restoring of deleted files. However, it’s not available when you delete duplicate files on external hard drive or other portable devices.

customize settings

The Image Similarity setting is applicable to the app’s Find Similar Image feature. If you want to find duplicate photos and the similar ones on your external hard disk, you can adjust the setting to meet your need. You can also specify file size for scanning.

Under Ignore List, you can exclude folders, subfolders and file extensions from scan. Suppose you need to look for the duplicate files on your external hard drive but want the scan to skip certain folders (or subfolders). The folder exclusion feature will be useful.

You can also enable or disable the Ignore Bundle and Ignore System Hidden Files and Folders options.

exclude folders or file extensions when looking for duplicate files on external hard drives

Cisdem Duplicate Finder for Mac uses MD5 value checksum algorithm and can do byte-by-byte comparison. This duplicate file finder and remover scans quickly and can find true identical files by content. It can provide Mac users with the best solution to find duplicate files on external hard drives.

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Manually find and remove duplicate files on external hard drive with Finder

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

You can also find duplicate files on external hard drive or Mac’s internal hard drive with Terminal. Note that it only finds 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.

Why there are so many duplicate files and how to avoid them

Why are there so many duplicate files on my Mac? It’s not uncommon to have duplicate files on your Mac 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 file, 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.

  • Delete photos and videos from SD card after you transfer them to your Mac
  • Set your Mac to detect duplicate files while importing
  • Be aware that resizing or editing photos will lead to almost duplicate files
  • Avoid unnecessary backups
  • Use duplicate file finder software on a regular basis

In conclusion

Above are the three common ways on how to find duplicate files on external hard drive on Mac. 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.

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5 Comments Leave a Reply

  • 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.

    2 years ago REPLY
  • 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?

    3 years ago REPLY
  • 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.

    3 years ago REPLY
  • 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.

    3 years ago REPLY
  • 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.

    3 years ago REPLY