If you are backing up your folders containing photos or videos or documents to another location, there is a great chance to copy the same content again and again. It is highly useful to determine what has changed between versions changes.
WinMerge is an Open Source differencing and merging tool for Windows. WinMerge can compare both folders and files and can present differences in a visual text format that is easy to understand and handle. The folder compare shows all files and subfolders found from compared folders as a list. Folder comparison allows synchronizing folders by copying and deleting files and subfolders.
You can use UltraCompare to compare files, folders, and texts. It offers two ay folder compare and it can compare three folders at a time. Folder Synchronization allows quickly sync different files between two folders, you can quickly locate duplicate files between two or more folders with UltraCompare. UltraCompare is available for Windows, Mac, and Linux.
FreeFileSync is a folder comparison and synchronization tool that creates and manages backup copies of files. Instead of copying every file every time, FreeFileSync determines the differences between a source and a target folder and transfers only the minimum amount of data needed. This open Source software, available for Windows, macOS, and Linux.