FreeFileSync compare and synchronize files.
FreeFileSync is a folder comparison and synchronization software (synchronization with MTP devices is supported) that creates and manages backup copies of all important documents. FreeFileSync determines the differences between a source and a target folder and transfers only the minimum amount of data needed.
FreeFileSync is a graphical file synchronization and folder comparison tool available for Windows, Linux and macOS. It main purpose is to speed up backup operations by examining the differences between source and target folders, and then only copy what is really needed rather than copy everything each time like disk cloning/imaging tools do.
FreeFileSync offers many useful functions. It allows you to work in 4 modes: automatic (changes detected and applied on both sides), mirror (the right folder will be overwritten with the contents of the left), updating (copying new or updated files to the right) and own (allowing the user to define own rules for synchronization).
The second core feature is folder comparison: With FreeFileSync, you can binary-compare entire folders and see exactly where the difference is. This is similar to what file diff tools do, but at a folder level.
Comparing data may take place in relation to the size and date of modification of the files and their contents. Of course, the user can carry out the process of synchronizing the contents of folders without first comparing them.
Since synchronization is usually very fast and can be automated by creating batch jobs, it is easy to always have your important files backed up in a second location.