FreeFileSync is a free, open-source file synchronization tool that helps you compare and synchronize folders on Windows, macOS, and Linux. Whether backing up to external drives, keeping multiple computers in sync, or maintaining mirrored copies, FreeFileSync automates the process reliably.
The comparison engine examines folder contents quickly, identifying files that are new, modified, or deleted on either side. File content comparison uses hash values for exact verification beyond timestamps. Multiple comparison variants handle different synchronization scenarios.
Synchronization options include two-way sync keeping both sides identical, mirror mode replicating source to target exactly, and update mode copying only newer files. Custom rules define exceptions for specific files or folders. Preview shows proposed changes before synchronization executes.
Real-time synchronization monitors folders continuously, immediately copying changes as they occur. Auto-sync combines folder comparison with synchronization in a single operation. Batch jobs save configurations for repeated use with scheduled tasks.
The filter system excludes files by name patterns, size ranges, and dates. Time shift handling corrects timestamp differences from daylight saving changes. File versioning moves replaced files to a backup folder rather than deleting permanently.
Additional features include handling locked files that other applications are using, copying NTFS security permissions, and logging operations for review. Parallel file copying maximizes performance on fast drives. Email notification reports batch job completion status. RealTimeSync companion application monitors folders and launches FreeFileSync automatically.