FreeFileSync
freefilesync.orgFree open source file synchronization and backup for every platform
Utilitiesfile-syncbackupopen-sourcecross-platformfolder-comparisonfile-management

About
FreeFileSync is an open-source folder comparison and synchronization tool available for Windows, macOS, and Linux. It intelligently detects differences between source and target folders and transfers only the changed data, avoiding redundant full copies. The project is sustained through donations and ad revenue, with a Business edition available for commercial use.
Problem
Manually keeping files and folders in sync across locations is tedious and inefficient, especially when copying everything each time wastes time and storage.
For
individuals and businesses who need reliable file backup and synchronization across platforms
How it works
FreeFileSync compares source and target folders to identify differences, then transfers only the minimum data needed to bring them into sync.
Business model
open-source
Status
launched