Delete Duplicate Files on External Hard Drive on PC and Mac: Steps and Tips

Duplicate Finder

Duplicate file finder for external hard drives

Free Download Windows 10 or later Free Download macOS 10.11 or later GET IT ON Google Play Download on the App Store

Summary

The easiest way to find and delete duplicate files on an external hard drive is to use Cisdem Duplicate Finder due to automatic duplicate detection and quick, reliable duplicate removal.

1. Download. Download and install Cisdem Duplicate Finder.
2. Scan. Use this app to scan your external hard drive or specific folders on it.
3. View. View duplicate files found by the scan.
4. Select. This app automatically selects all duplicates for deletion and lets you make adjustments.
5. Delete. Click Delete to remove all selected files and confirm the removal.

All duplicates are now deleted, and the original files are kept.

Free Download Windows 10 or later Free Download macOS 10.11 or later

If you only have a small number of files in external hard drive, File Explorer on Windows or Finder on Mac can also help. They can help you sort files by name and size, but you still need to compare the file contents manually.

This guide covers both the automatic and manual methods on Windows and Mac, helping you remove duplicate photos, videos and other files from your external hard drives.

How to Find and Delete Duplicate Files on External Hard Drives Automatically

This method works on both Windows and Mac and uses Cisdem Duplicate Finder - an AI-powered duplicate file and photo finder. It compares file content to identify true duplicates, and automatically selects duplicate files for bulk removal. You can preview the results and adjust the selections before deleting files from your external hard drive.

What Can Cisdem Duplicate Finder Do?

Steps

Step 1: Download and install Cisdem Duplicate Finder

Download and install Cisdem Duplicate Finder on your Windows or Mac computer. Open the app.

Free Download Windows 10 or later Free Download macOS 10.11 or later

Step 2: Add your external hard drive(s)

Connect the external hard drive to your computer. Under Local File Scan, add the entire drive or or specifics folder where you want to find duplicate files. Click Scan Now.

Step 3: Review the scan results

When the scan is complete, the results window will appear. The All tab displays all found duplicate files, and other tabs (such as Image) lets you view duplicates by type.

You can also switch between view modes, search for files by name, and sort the results by name or size.

Step 4: Select the duplicates for removal

By default, Cisdem Duplicate Finder automatically selects duplicate files for removal, leaving one copy unselected in each group.
You can also manually select or deselect files, or apply a selection rule to multiple groups at once.

Step 5: Remove the selected duplicates

After confirming that the correct files are selected, click Delete. Click Yes in the confirmation message to remove them.

I also made a video tutorial to guide you through this entire process.

Tips

Tip 1. Protect your important folders and files

It's likely that your external hard drive has some important data that you want to keep untouched. You can easily protect them! Before clicking Scan in step 2, go to Settings to add your important folders and files that you don't want to scan to the Ignore list, such as your backups.

Tip 2. Effectively delete duplicate photos on your external hard drive

Technically, duplicate photos are exactly identical, regardless of their names. However, some people may also consider similar photos as “duplicates”. If you want to handle these on your external hard drive, make sure Enable similar images function is selected in Settings.

Cisdem Duplicate Finder uses AI-powered similarity detection engine can find visually similar photos even when they have different file names, formats, or contents.

Tip 3: Reduce the scan time by narrowing the scan scope

If you do not need to scan every file on the drive, you can adjust the settings to reduce the scan scope. For example, you can turn off similar image detection, set a minimum file size, ignore certain folders, or exclude specific file formats. I tested two sets of scan settings on the same external hard drive containing 9.27 GB of files:

Tip 4. Remove duplicates from your Photos library stored on an external drive (Mac)

If you are a Mac user in this situation, extra actions may be required to complete step 2.

1. Double-click your Photos library directly on your external hard drive, which will open the library in the Photos app.
2. In the Photos app settings, click the Use as System Photo Library button. (Ignore this tip if this button appears gray, which means the library is already the system one.)
3. Now you can add the Photos library and click the Scan button.

How to Manually Find and Delete Duplicate Files on an External Hard Drive

If there aren’t many files on your external hard drive, there’s an alternative method, with which you look for and eliminate duplicates by hand.

The method requires the use of the built-in file manager on your computer: File Explorer (Windows) or Finder (Mac). These built-in tools can help you filter and sort files by type, name, and size, making potential duplicates easier to find. However, they do not automatically compare file content. They may miss duplicates with different names.

Use File Explorer (Windows)

Here’s how to find duplicate photos on your external hard drive and delete them with the help of File Explorer.

Step 1: Connect your external hard drive to your computer.

Step 2: Open File Explorer, find the drive in the Navigation pane on the left, and open it.

Step 3: Filter photos by typing kind:=picture in the search bar in the top right corner. Now the File Explorer window only displays all photo files stored on your drive.

Step 4: Select View > Details, then select Sort > Group by > Name (or Size). Now it becomes easier for you to discover photos with the same name or size, which are potentially duplicates.

Step 5: Go through photos to find duplicates by comparing their contents, names and sizes. Right-click the duplicates that you have found and select Delete to move them to the Recycle Bin.

Continue handling other types of duplicates in a similar way.

Use Finder (Mac)

Follow the steps to use Finder to look for duplicate files on your external hard drive and clean them up.

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

Step 2: Open Finder, find the drive in the sidebar on the left, and open it.

Step 3: Filter photos on the drive.

• Press Command + F to bring up the advanced search in Finder.
• In the first drop down menu, choose Kind. Then choose the Image file type from the dropdown menu. You can further choose a specific image format (such as JPG) if needed.
• Now the Finder window only lists all photos stored on your drive.

Step 4: Experiment with different sort orders and view modes until it becomes easier for you to spot potential duplicates.

Step 5: Manually identifying duplicates by closely comparing photos. Select the unwanted duplicates, control-click, and then choose Move to Trash.

Now you can handle another type of duplicates in a similar manner.

Conclusion

Why do you have duplicate files on your external hard drive? There can be various reasons. For example, duplicates already existed in the files that you backed up to the drive. Moving files by copying and pasting instead of using drag and drop also creates duplicates.

Luckily, you can easily remove those duplicate files from your external hard drive by using software. The process is easy and quick and lets you rest assured that duplicates are correctly identified and safely deleted.

In addition to regularly cleaning up duplicates, you can try preventing them from appearing in the first place, such as by avoiding necessary backups, using drag and drop, or naming your files in a logical way.