Frequently Asked Questions

1. General
   • What are the basic steps to use FreeFileSync?
   • Where can I find information about FreeFileSync's advanced features?
   • Which features make FreeFileSync unique?
   • Which operating systems does FreeFileSync support?
   • Are there limitations on the number of files to sync?
   • Is FreeFileSync free for commercial use?
   • May I distribute the FreeFileSync installation package?
   
   
2. Installation
   • Do I need to uninstall FreeFileSync before installing a newer version?
   • Should I use local or portable installation?
   • Why does FreeFileSync show an advertisement in its installer?
   • Does FreeFileSync install advertised software silently?
   • Is there a version of the FreeFileSync installer without advertisements?
   • How can I get the Donation Edition for multiple users?
   • My virus scanner/firewall shows a scary warning dialog.
   
   
3. Troubleshooting
   • How can I report bugs or suggest new features?
   • Why does Windows Explorer show a different number of items?
   • How can I fix the error "Cannot read/write permissions of <file path>"?
   • Why are some files still different after synchronization?
   • I have deleted files accidentally. How can I restore them?
   • FreeFileSync has crashed/is hanging! How can I help with trouble shooting?
   • How can I record a trace file for troubleshooting file access errors?

General

1. Choose left and right directories.
   

    

2. Compare them.
   

    

3. Select synchronization settings.
   

    

4. Press Synchronize to begin synchronization.
   

For the most up to date description of FreeFileSync, visit the Online Manual. Press F1 while running FreeFileSync.

If internet access is not available, an offline version of the manual can be found in the FreeFileSync installation folder.

After you've become comfortable with using FreeFileSync, be sure to read chapter Tips and Tricks!

• Synchronize folders on network shares and local disks
• Synchronize mobile devices via MTP (Android, iPhone, tablet, digital camera)
• Synchronize cloud storage via SFTP (SSH File Transfer Protocol)
• Free FTP client: synchronize via FTP (File Transfer Protocol) and FTPS (SSL/TLS)
• Detect moved and renamed files and folders
• Manage versions and keep a history of deleted/updated files
• Show disk space usage for a directory tree
• Copy locked files (Volume Shadow Copy Service)
• Detect conflicts and propagate deletions
• Compare files by content
• Configure handling of Symbolic Links
• Automate sync as a batch job
• Process multiple folder pairs
• Comprehensive and detailed error reporting
• Copy NTFS extended attributes (compressed, encrypted, sparse)
• Copy NTFS security permissions
• Copy NTFS Alternate Data Streams
• Copy HFS+ extended attributes and ACLs
• Support long file paths with more than 260 characters
• Fail-safe file copy prevents data corruption
• Cross-platform: Runs on Windows, Linux, macOS
• Expand environment variables like %UserProfile%
• Use macros %time%, %date%, et al. for recurring backups
• Access variable drive letters by volume name (USB sticks)
• Native 64-bit support
• Prevent disc space bottlenecks via optimal sync sequence
• Full Unicode support
• Highly optimized run time performance
• Include and exclude files via filter
• FreeFileSync portable and local installation available
• Handle daylight saving time changes on FAT/FAT32
• Case-sensitive synchronization
• Serialize multiple users accessing the same (network) folder via folder locking
• Fully localized user interface available in 30+ languages
• ... download and use for free!

FreeFileSync runs natively on all 32 and 64-bit Windows versions.
FreeFileSync runs on all recent 64-bit editions of macOS.
FreeFileSync is supported on all major Linux distributions.

	Microsoft Windows		Apple macOS		Linux
	Windows 10 Windows 8.1 Windows 8 Windows 7 Windows Vista Windows XP		macOS 10.12  – Sierra OS X 10.11  – El Capitan OS X 10.10 – Yosemite OS X 10.9 – Mavericks OS X 10.8 – Mountain Lion		Ubuntu Debian openSUSE CentOS

FreeFileSync imposes no artificial limitations on how many files you can sync. Practically speaking, the only limiting factor for extremely large sync jobs is the amount of free memory available: For each 1 GB of RAM, FreeFileSync can synchronize roughly 1.7 million file pairs at a time.

Yes, FreeFileSync may be used in business, commercial, and government environments without cost.

You are permitted to distribute the software subject to the following conditions:

Installation

No, you can safely install a new version of FreeFileSync into a directory that contains an old version. FreeFileSync will recognize the previous installation and clean up thoroughly should you choose to uninstall at a later time.

FreeFileSync is designed for local installation and provides the best user experience in this variant.
In order to support restricted scenarios, FreeFileSync also allows for portable installation on USB memory sticks or external hard drives. However, part of FreeFileSync's functionality may not be available in this case: For example, it won't be possible to manage FreeFileSync configuration files via context menu in Windows Explorer or start batch runs with a few mouse clicks. Therefore local installation is recommended in general.

The FreeFileSync installer is showing a single advertisement (and only during installation) to help recover part of the software development effort, which is the time and energy invested in application design, implementation, and continuous support. Although it's nowhere near enough to allow to focus on FreeFileSync full time, it is more effective than asking for donations only. If nothing else, it helps keep up the motivation for the project, and, next to our other big motivation: striving for perfection in software design.

No, FreeFileSync never installs anything without consent. During installation you are provided a single offer screen. If you want to support the FreeFileSync development or find the software that is shown useful, feel free to accept the offer. If not, just decline and nothing other than FreeFileSync will be installed.

	Standard (Ad-Supported)	Donation Edition
Sync files without limits
Ad-free installation
Auto-updater		(Windows)
Portable version (ZIP)
Silent installation
Price	Free	You decide

Donation Edition Bonus Features

The FreeFileSync Donation Edition may be used and installed by a single home user on their computer. This includes installation on portable storage devices (USB memory sticks) and even use on different computers, provided that FreeFileSync was already activated (during first start) on the former computer.

However, if the portable installation files are copied to a different computer (instead of being used directly from a memory stick), this is considered to be a second installation.

In order to obtain the FreeFileSync Donation Edition licensed for multiple users/installations, please use the donation button here on the side.

No, the FreeFileSync installer never contains malware or viruses. Both firewalls and virus scanners work with heuristics in addition to searching for known virus patterns. Heuristics are generic algorithms that try to identify malicious behavior by evaluating certain program characteristics according to their proprietary implementation. Often, it is already sufficient to have a program access the registry or the internet to get this classification. By their very nature, heuristics cannot be exact and frequently lead to false positive detections. Occasionally FreeFileSync is a victim of this.

In practice, however, one can distinguish real malware threats from heuristic alert as they contain phrases like *gen*, *generic*, *heur*, *heuristic* or *reputation* as part of the threat signature name, for example Trojan.Win32.Generic!BT or Heur.AdvML.B or WS.Reputation.1.

Additionally, certain anti-virus products will not only warn about viruses, but will also flag advertisements like the one shown in the standard FreeFileSync installer. The warning dialogs misleadingly use the same layout as would be used for viruses and trojans. In these cases the only way to tell what the AV software is actually complaining about is, again, to look at the threat signature:
If an advertisement is detected, a signature including *PUA* is used, which is short-hand for possibly unwanted application. For example PUA.InstallCore. In other cases a more descriptive term like *adware* is used. These warnings can safely be ignored since the software advertised in the FreeFileSync installer is always optional.

In any case, when in doubt never trust a single anti-virus software and use an online mass virus scanner for comparison.

Troubleshooting

The best place to get in contact is via the FreeFileSync Forum. This allows for other FreeFileSync users to share their experience and give immediate feedback. A lot of problems have already been discussed and solved, so searching the forum may be the quickest way to get help.

When synchronizing with FreeFileSync and comparing the number of items of the source and target folders with Windows Explorer, consider the impact of the following settings.
If you still find yourself unable to explain the difference, drill down into specific mismatching folders with both applications until you find an actual file/folder that is handled differently. This should reveal what the problem is.

• Filter settings: FreeFileSync's default filter settings exclude a few items that are generally not relevant for synchronization, like the Recycle Bin or desktop.ini, thumbs.db files.

   

• Symlink settings: By default FreeFileSync skips symbolic links.

   

• Ignored errors: Check if FreeFileSync reported errors during comparison or synchronization.

   

• Long file paths: Unlike FreeFileSync, Windows Explorer is not able to handle file paths longer than 260 characters. Consequently, Explorer will not count files/folders with such long paths.

Copying NTFS permissions is not needed in general and is best left disabled. Go to Menu → tools → options and ensure permission copying is unchecked.
If you are an administrator and really need to preserve DACL, SACL, Owner and Group permissions, make sure the FreeFileSync process is running with admin rights.

Certain anti-virus products, for example Comodo v8, write hidden alternate data streams to newly created files. Unfortunately, this has the side effect of also setting the file modification time to the current time. Since this happens after FreeFileSync has copied the files, the next comparison will detect this modification just like any other external change.
To resolve this problem, file a bug report on the anti-virus software's support web site, use a different anti-virus software that does not modify files, or look for options to disable such features (e.g. disable Comodo's "File Source Tracking").

This depends on how you have set up deletion handling in synchronization settings:

• Permanent: You can try to recover them using a file un-deletion tool. Depending on whether the physical memory blocks on the hard drive have been overwritten in the meantime, it is possible to partially or even fully restore the files.

   

• Recycle Bin: The deleted files are in the Recycle bin, unless they were flushed out by newer files that were moved to the bin later.

   

• Versioning: The deleted files are in the directory you have set up.

Usually, FreeFileSync will generate a mini dump file automatically when it detects a program crash. This file can then be sent to the FreeFileSync development team for further analysis.
In some situations this will not work correctly, for example, if the process is hanging for a long time rather than crashing directly. In this case, you can create a dump file manually as follows:

Download the tool Process Explorer and reproduce the crash/hang. Now start Process Explorer and right-click on FreeFileSync_x64.exe (or *_win32.exe if you're on 32-bit Windows), select Create Dump and then Create Full Dump. Next, compress this file with zip or rar and send it to the email shown in FreeFileSync's about dialog.

If creating the dump file fails with Access denied, check that Process Explorer is running with elevated rights: Menu → File → Show Details for All Processes