In our previous articles, we were talking abouthow to check free space on Mac and  5 steps to free up hard drive. On this page, we are going to review in more detail one of the disk space eaters – duplicate files and folders.

1. Find Duplicates Manually

If you are trying to find duplicates on Mac manually, you may realize that it’s not that simple. You can sort files in the Finder by types (name, extension, size, etc.) and review all the files one after another. For that you would need to create a Smart Folder.

  1. Open Finder and use Command+Option+N shortcut.
  2. In a right top bottom click Plus button.

New Smart Folder on Mac

Here you can choose the kind of files and folders you want.

Drop-down menu for choosing kind of files

Drop-down menu for sorting files

If you don’t see the criteria you need, click “Other…” and select the attribute for a search.

Choosing attribute for a search in Smart Folder

Now open each file that has the same name or size and check for duplicates.

Smart Folder showing files with the same size

Well, as you see, it’s better not to lose time and use the duplicate cleaner. Let’s see how to remove duplicate files easily and quickly.

2. How to quickly find duplicates on Mac with Duplicate File Finder

We can’t imagine how many identical images, videos and other types of files are on our computers. And if there is more than one Mac user, then you can be sure the same music, photos or documents are kept on disk. Double files may take up significant space in your hard drive. But don’t worry. Here is the best software to remove duplicate files – Duplicate File Finder.

Duplicate File Finder is an app to delete duplicate files on Mac and is Free to Download. You can compare two or more folders/hard drives to duplicate files and delete the same files.

This duplicate file cleaner has a set of awesome features:

  • Animation of scanning process
  • Chart visualization of duplicates
  • Sorting of files by size, type, name
  • Adding of files and folders to Skip List
  • Ability to choose folders in which to delete duplicates and those in which to keep them untouched
  • Built-in intelligent cleanup tips
  • Scanning any external drive
  • Built-in search
  • Finding hidden duplicate files
  • Finding similar pictures
  • Merging similar folders
  • And many more!

Duplicate File Finder showing scanning results

3. The algorithm for searching for duplicates

Before checking files for identity by their data, the algorithm for finding duplicate files uses two main characteristics – sizes and extensions of the files. This means that If two or more files with the same extensions have the same size, they are then compared by their data. The filename is not taken into account. Users often rename files, so identifying duplicates by name is not reliable. Furthermore, different files might often have the same name.

For example, If there are two identical files with img.png and myphoto.PN, they will be displayed as duplicates. However, if two files differ from each other in size – even by one byte – they will not be displayed in the application.

Duplicate photos
With the app, you can find duplicate files in several different folders or even hard disks per single session.

You should just click the “Plus” button or select and drag and drop several folders you want to scan for duplicates. It is possible to scan even the whole disk.

Folders selected for scanning with Duplicate File Finder

4.There are three possible common scenarios for removing duplicate files:

1. Find duplicates for a particular file.

Select one or several folders to scan → when the scanning is completed, switch to the Duplicate Files panel → enter the filename in the filter (all other files and folders will be hidden) → select your file → preview its duplicates → remove unneeded duplicates. If you need to find a specific file among all the duplicates quickly, you can also use the filter option “Sort by name.”

2. Find and remove biggest duplicates to free up disk space.

  • Take a look at Cleanup Hints (list of quick tips to select and remove the biggest duplicate files). Even if you are working with this duplicate file software for the first time, you will find it extremely helpful.
  • Or switch to the Duplicate Folders panel and remove duplicate folders.

3. Find duplicate files and remove them one by one.

Scan the folder(s) → switch to any category and preview your duplicate files → select duplicates one by one, previewing them → click the Review & Remove button. This is the longest way.
However, you may prefer to preview each file and decide which ones to delete.

Features highlighted in Duplicate File Finder
Features highlighted in Duplicate File Finder window

5. Similar folders

It can happen that you have different folders that keep both duplicates and unique items. Duplicate File Finder has unique features; it can find not only duplicate folders but even similar folders – the folders that have both duplicates and at least one unique file. For example, Folder A contains file1, file2, file3 and Folder B contains file1, file2, file3, file4. There are three duplicate files and one unique file. Duplicate File Finder will show you these folders under the Similars tab. Take a look at such Similar folders and remove the “space eaters.”

Similar folders section of Duplicate File Finder

6. The fastest way to select duplicates from a specific folder

This scenario may suit you the best if you want to scan two different folders/disks and remove duplicates from one of them. You can also

Go to the app Preferences → switch to the Auto Select panel → add to the Always Select list a folder from which you want to remove duplicates → add to the Never Select list a folder in which you want to keep duplicates as originals → rescan the folders → click the Auto Select button (all duplicates specified in Always Select will be selected) → review them and click to Remove.

Skip list section of Duplicate File Finder Preferences

The Auto Select feature is a reliable way to speed up the selection of tons of duplicates. You can also use a command “Select All Copies in …” from the context menu and specify a particular folder for duplicate removal. Or use a reverse command “Keep All Copies in …” that will select files in all folders except the specified one.

In the app’s Preferences you can find some more helpful setting possibilities. For example, by default, the application skips the smallest files to make scanning fast. If you want to scan all the files, including the smallest ones, go to the General tab and select “Check all files.” Also, you can manually set up the minimal file size to be scanned.

By default, the app does not check files in hidden folders, however, you can do it by changing settings in the Preferences. And even setting up the files’ extensions that should not be scanned is possible.

General section of Duplicate File Finder Preferences
Skip list section of Duplicate File Finder Preferences
Remove section of Duplicate File Finder Preferences

7. What if the duplicates cannot be removed?

Sometimes you may get a message that the app cannot remove duplicate files. There are several reasons for this:

  1. You are trying to remove files from an external drive which is mounted as Read Only. For example, you mount NTFS external disk and don’t have a special driver to make the disk writable on Mac. You should, therefore, install the necessary extension to allow removal of the duplicates.
  2. You are trying to remove files from the external volume that does not have the Trash folder as yet. By default, Duplicate File Finder moves files to the Trash. If no Trash folder has been created, the app does not have enough permission to remove a file. You should switch to Finder window and from there remove any unneeded file on that external drive/volume. The Trash for external volume will then be created, after which Duplicate File Finder can remove identical files.
  3. Your files might be locked. Check file permissions – select a file/ folder in the Finder, use CMD+I shortcut to verify the permissions.
  4. Your files might be used by another application.

Read a detailed guide on how to troubleshoot situations when duplicates can’t be removed.


In conclusion, it should be said that if you have the time and interest, you can use the first method – find and remove duplicates with Finder. However, if you are looking for an easy program to find duplicate files, then use the duplicate cleaner mentioned above. You can use its free version to finds all duplicate files on your Mac. If you want more features, you can use in-App purchase Upgrade to Pro.

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