FreeFileSync is a free, open source folder comparison and synchronization software for Windows and Linux. It also works on 64bit operating systems on both platforms. The program can be installed in two versions: as a standard installer on Windows or as a portable application (no registry entries). Powered by a clean, easy, intuitive interface, this tool offers a myriad of features for synchronization purposes.

Key Features
* Detect moved and renamed files and folders
* Copy locked files (Volume Shadow Copy Service)
* Detect conflicts and propagate deletions
* Binary file comparison
* Full support for Symbolic Links
* Automate sync as a batch job
* Process multiple folder pairs
* Copy NTFS extended attributes (compressed, encrypted, sparse)
* Copy NTFS security permissions
* Support long path names > 260 characters
* Fail-safe file copy
* Comprehensive and detailed error reporting
* Cross-platform: Windows/Linux
* Expand environment variables like %USERPROFILE%
* Access variable drive letters by volume name (USB sticks)
* Native 64-bit support
* Keep versions of deleted/updated files
* Optimal sync sequence prevents disc space bottlenecks
* Full Unicode support
* Highly optimized performance
* Include/exclude files via filter
* Local and portable installation
* Handle daylight saving time changes on FAT/FAT32
* Use macros %time%, %date%, et al. for recurring backups
* Case sensitive synchronization
* Built-in locking serializes multiple jobs running against the same network share
* Those are just a couple of its features (not all), there are many others that are improved and added constantly.

Changelog v5.16
* Integrated both category and sync action view into middle grid
* Condensed folder pair display names on overview panel
* Consider symlinks and junctions when copying locked files (Windows Vista)
* Resolved failure to set directory lock within Windows XP as Virtual Box guest
* Period resolves to working directory again
* Fixed "DecodePointer could not be located in KERNEL32.dll" (Windows 2000)
* Support closing progress dialog forcefully during sync (OS X)
* Don't disable all child items if directory traversal fails for a single item only
* Simplified deletion confirmation dialog (removed "delete on both sides")
* Work around wxWidgets leaking memory on exit (OS X)
* Avoid wxWidgets crash when deleting folder pair control (OS X)
* Prevent wxWidgets corrupting stack when wxLocale is allocated statically (Linux)
* Use GetUserDefaultLangID to determine installer default language
* Avoid progress speed and remaining time jitter
* Check existence only once for duplicate base directories
* Detect invalid file symlinks pointing to directories
* Disable unsuitable buttons in pop up dialogs when checkbox is set
* Copy folder attributes if source is a junction already on Windows XP instead of Vista
* Mark failed UTF conversions with replacement character
* Do not restore main dialog position outside visible screen area (multi monitor setup)
* Support detection of moved files through symlinks
* Reduced memory consumption when detecting moved files
* Check for duplicate file ids when detecting renamed files
* Redetermine volume id for followed directory symlinks
* Removed "Compare_Complete.wav"
* Don't accept file deletion confirmation in less than 50ms
* Systematically resolved translation bugs
* Added Serbian language