Duplicate File Finder is an application to find duplicate files and folders on a Mac computer. The following document aims to bring the technical details of duplicates search and some restrictions of the app to your attention as well as provide you with valuable information so that you can strike the best results and performance when cleaning duplicates on your Mac.


System requirements for Duplicate File Finder

  • macOS 10.10 or later
  • 64-bit processor
  • 30 MB free disk space
  • 4 GB RAM

Files and Volumes Support

Duplicate File Finder scans any type of volume:

  • Internal Mac hard drive
  • External Drives
  • Network Disks
  • Separate folders on internal and external drives
  • Synchronized folders from Cloud storages on a Mac

Duplicate File Finder finds duplicates of any file type:

  • Photos
  • Music
  • Video
  • Documents
  • Archives
  • Folders
  • And others

Duplicate File Finder DOES NOT find the following types of duplicate files:


Family Sharing

As Family Sharing does not work with in-app purchases, Duplicate File Finder does not support this option. Learn the explanation about Family Sharing on the Apple Support page.

You can use Duplicate File Finder Pro on another your Mac using the same Apple ID, you used to purchase the application. Please note, when you install the app on a new Mac computer, your license for the Pro version on the app, does not synchronize automatically. You need to use the Restore button on the Purchasing dialog window to upgrade Duplicate File Finder to the Pro version.


Finding Duplicates in the Photos App and Photos Library

Duplicate File Finder is an app to find duplicate files on regular folders and disks. The app is not intended to find identical images inside the Mac Photos and Photos Library because all pictures there are kept inside special packages. Nevertheless, you can scan the photos if you unfold the package and select images from its subfolders. Learn more >>


Duplicate Searching Algorithm

Duplicate File Finder compares files accurately using three main characteristics – their sizes, extensions, and binary data. In the first step it finds the files of the same file extension type, then it compares their sizes. If two or more files with the same extensions have the same size, they are then compared using their binary data. The application never takes the filename into account because computer users can always rename identical files or give different files the same name, so the results would not be accurate. Duplicate files are files, which have an identical type, size, and binary data. Learn More >>


Duplicates Scanning Speed

The scanning speed of the app depends on the following factors:

  • The number of duplicate files.
  • The total size of scanned folders/volumes.
  • The scan speed of the disk.
  • The app’s scan preferences.

If you scan an external disk with a huge number of files and the disk is connected to your Mac via USB2.0, the scanning time may take up even several hours. You can decrease the scan time using some tips and settings in Duplicate File Finder. Learn more >>


Features Available in Free and Pro Modes

Duplicate File Finder provides two modes: Free and Pro. The Pro mode is available with In-App Purchase and gives you more possibilities for a quick duplicates cleanup on Mac. When you upgrade the application to the Pro mode, the name of the app Duplicate File Finder will be changed to Duplicate File Finder Pro.

Free mode version features:

  • Detection and listing of all duplicate files and folders.
  • Removal of duplicate files
  • Support of any drive type supported by macOS.
  • QuickLook option to preview duplicates.
  • Option to view the duplicate files directory and quickly open them in the Finder.
  • Auto-Select feature.
  • Skip List feature.
  • Sorting of duplicates by different categories (type, name, count, path, size).
  • Regulating the size of files that should be scanned.
  • Cleanup hints section.
  • Preview removal history.

Pro mode version features:

  • The Pro mode provides all the options of the free version and has some great additional features:
  • Removal of duplicate folders.
  • Similars Tab (operating similar folders – folders which contain both duplicate and similar files.)
  • Support of hidden duplicate files.
  • “Merge Folders” option. The ability to merge the content of Similar folders.
  • “Select Duplicates in Folder” option.
  • “Restore removed duplicates” option.

Duplicates Removing

After duplicates selecting and clicking to remove them, Duplicate File Finder displays a confirmation screen with a list of all selected duplicates. Please, check them carefully and make sure you don’t need them anymore. And only then confirm the removal of them.


Merge Folders Option

With Duplicate File Finder you can review Similar folders and merge them. Similar folders are the folders which contain both duplicate and identical files. Please note, the Merge option is available only for Similar folders and only in the Pro mode. Learn more >>


How does Auto Select work?

  1. Duplicate File Finder checks if scanned duplicates are still alive (as you could delete them after the scan, e.g. from Finder).
  2. Duplicate files then are checked with Never Select and Always Select lists. If they are presented there the app does skip or select files respectively.
  3. The program selects files that have similar names like: “Copy of filename”, “Filename – 2” or “Filename (2)”.
  4. If the files have identical names the app goes up and checks folders by the same scenario.

Note, the app always keeps one original file. You can navigate to duplicates group and click arrow right to Auto Select button highlighted red. And choose one of the options: Auto select oldest and Auto select newest.


Removing all duplicate files entries, including the original file

By default the option to select and remove all duplicate copies is disabled. When you select files, the program keeps one file as original. But you can change this option in the Preferences → Remove tab. Also, if you try to select all duplicates, you will see a notification asking you to allow removing all duplicate copies.


Resolving Issues when some duplicates cannot be removed

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

  • 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 system extension (NTFS driver) to allow removal of the duplicates. Learn more >>
  • You are trying to remove files from an 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. Another solution for such an issue is to remove files or folders permanently. In this case, Duplicate File Finder will require your confirmation to delete files permanently. If it suits you, confirm the removal. Learn More >>
  • Your files might be locked. Check file permissions – select a file/ folder in the Finder, use CMD+I shortcut to verify the permissions. Learn more >>
  • Your files might be used by another application.

Upgrading to Pro Issue

Note, if, after the purchase, the app hasn’t upgraded to Pro, you should restore the app. It may sometimes happen because of an unstable internet connection or Apple Service needing more time to process the transaction. Reboot your Mac → go again to Upgrade to Pro → and click the Restore button.


Restoring Removed Duplicates

Sometimes it may happen when you remove both copies of your files and need to retrieve them back. Duplicate File Finder provides a special option to restore removed duplicate files.

To Retrieve duplicates, go to the Menu Bar → Duplicate → select Restore Removed Duplicates.
Here you can choose any date session and view which files were deleted on this date. If the files are in the Trash folder, you are able to restore them.

*Please note, that when you remove files by Duplicate File Finder, the program moves them to the Trash. However, this option is changeable. That’s why you need to check it in the Preferences → Remove section → a point “Remove Duplicates permanently.”

**The Restoring option is available only in the Pro mode.


Learn More About Duplicate File Finder