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


System requirements for Duplicate File Finder

  • macOS 10.12 or later
  • 64-bit processor
  • 35 MB free disk space
  • 4 GB RAM

Files and Volumes Support

Duplicate File Finder scans any type of volume:

  • Built-in Mac hard drive
  • External Drives of HFS+(Mac OS Extended), APFS, FAT32, exFAT, NTFS formats
  • 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 also finds Similar Photos – pictures which look alike but they are not 100% identical.

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

  • Emails
  • Contacts
  • Calendar notes

Family Sharing

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

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

*If you downloaded Duplicate File Finder from our website, you can use one license key on two Mac computers.


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 >>

Note that if you have duplicate folders (folders with identical content), the duplicate files from these folders will not be displayed in the list of All Duplicate Files. You can view and operate this content in the Duplicate Folders section. If you have empty folders with the same names, they will be also detected as duplicates.


Duplicates Scanning Speed

The application scanning speed depends on the following factors:

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

If you scan an external disk which has a huge number of files and the disk is connected to your Mac via old USB2.0, the scanning time may take up to 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.
  • Support for searching hidden duplicate files
  • 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.
  • Finding similar photos

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 scanned folders.
  • “Select Duplicates in Folder” option.
  • “Restore removed duplicates” option.

*If you downloaded the trial version of Duplicate File Finder from our website, you can use all the Pro features for 3 days. Then you can decide to use the app in the Free mode, or upgrade to the PRO mode when needed.


Duplicates Removal

After selecting duplicates 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 their removal.


Merge Folders Option

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


How does Auto Select work?

The Auto Select option allows you to automatically select duplicates in bulk with one click according to the rules you set up in the Preferences. Here is the list of settings you can configure for the Auto Select option:

  • Always select – choose the folders in which all duplicates will be automatically selected.
  • Never select – choose the folders in which all duplicates will be skipped and never be automatically selected.
  • Suffixes in names – when you duplicate files, by default the system adds the suffix “copy” to the file name or adds a number to its name. So in this section, you can set up to automatically select files with such suffixes or add your personal suffix.
  • Prefixes in names – you can set up to automatically select files with such prefixes or add your personal prefix.
  • Select in Photos Library – choose whether to automatically select duplicates inside or outside the Photos Library.
  • Select by full path – choose whether to automatically select duplicates in alphabetical order or reverse alphabetical order of full path.
  • Select by name – choose whether to automatically select duplicates by names in alphabetical or reverse alphabetical order.
  • Select by parent folder – choose whether to automatically select duplicates by parent folder’s name in alphabetical or reverse alphabetical order.
  • Select by full path length – choose whether to automatically select duplicates in the shortest or longest path.
  • Select by name length – choose whether to automatically select duplicates with the shortest or longest names.
  • Select by parent folder name length – choose whether to automatically select duplicates with the shortest or longest names of their parent folders.
  • Select by modification date – choose whether to automatically select duplicates modified earlier or later.
  • Select by nesting level – choose whether to automatically select duplicates located in deep or high hierarchies.

Also, you can quickly set up some rules for the Auto Select option without a need to go to Preferences. Just navigate to the duplicates group and click the arrow right to the Auto Select button. Here you can choose one of the options: Auto select oldest and Auto select newest. This will help you to quickly select the needed duplicates inside groups.

*Note, when you use the Auto Select option, by default the app always keeps one original file. However, this rule can be changed in the Preferences → Advanced tab, where you could enable the option to allow removing all the duplicates. So check this setting before using the Auto Select option.


Removing Duplicates options

By default, when you select and remove files with Duplicate File Finder, the program keeps one file as the original. But, if for some reason you want to remove all copies of duplicates, you can set such a possibility in the PreferencesAdvanced tabAllow removing all duplicate copies. After this, you will be able to remove both duplicate and original files. Also, if you try to select all duplicates, you will see a notification asking you to confirm this.


Resolving Issues when some duplicates cannot be removed

Sometimes you may get the 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 have mounted the NTFS external disk and don’t have a special driver which could allow you to write to the disk. 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 a Trash folder as yet. By default, Duplicate File Finder moves files to Trash. If no Trash folder has been created, the app does not have enough permission to remove the files. You should switch to Finder application 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, have Read Only permission or be located in a folder or on a disk with lack of permission. Check file permissions – select a file/ folder in the Finder, use CMD+I shortcut to verify the permissions. Learn more >>
  • Your files might be in use by another application.

Upgrading to Pro Issue

Note, if after the purchase, the app hasn’t upgraded to Pro, you should restore the In-App purchase. This 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 that you’ve removed duplicates and need to restore them. Duplicate File Finder provides a special option to restore such removed duplicate files.

To Restore duplicates, go to the application Menu BarDuplicate → 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 will be 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 this in the PreferencesRemove section → a point Allow removing all duplicates.

**The Restoring option is available only in the Pro mode. Note, that restoring files is possible only if they were deleted to Trash or they have copies on your Mac from which they can be restored. However, restoring removed files cannot be 100% guaranteed in some cases.