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.

FreeFileSync 5.21
* Detect moved/renamed files in mirror and custom variants
* New database format for two way variant: old database files are converted automatically
* Support double-clicking ffs_gui/ffs_batch files (OS X)
* Integrated search panel (Ctrl + F, F3) into main dialog
* Merged variant names into top button labels
* Hide dock icon while minimized to notification area (OS X)
* New keyboard shortcuts: F5, F6, F7, F8, F9, F10
* Further reduced size of database files by 10%
* Fixed Outlook *.ost files found missing on VSS snapshot volumes
* Added include filter context menu option
* Correctly scroll to search hits on different grid
* Always remove .ffs_tmp files permanently
* Fixed layout for buttons with text and graphics for RTL languages (Arabic, Hebrew)
* Revised file filter parser: new syntax for excluding items in subdirectories
* Improved configuration merge algorithm
* Fixed crash when showing help due to wxWigets 64-bit bug in help component (Windows 8)
* Avoid progress dialog graph flicker during resize when too few samples are available
* Progress status when deleting files not greyed out anymore
* Increased time-out to 20 seconds when checking for directory existence
* Exclude broken symlinks via filter before showing error message
* Follow symlinks when checking file/directory existence (Linux)
* Consistently set batch error codes during startup phase
* Updated translation files