FreeFileSync

I'm looking for a backup software that simply compares my current state (drive or folder) to the backup copy I made previously. I don't want to duplicate my data so I started to look for something that can do comparison, not simply copy over it without overwriting like I used to do.

The safest (lossless but bulky) way I used to do it, was to copy my current folder into its backup and just skip all files that are found. That was I simply add to it, without overwriting.

It's wasteful and at some point I have to stop kicking that can down the road.

I've been searching until I found something called FreeFileSync. It claims to be open source and free, but since I couldn't locate its source code and security checks I will simply not label it as such for now.

Here's their website: FreeFileSync: Open Source File Syncronization
Here's their youtube tutorial playlist: FreeFileSync Tutorials

So far it seems I can add or more pairs of directories to it, and run a comparison (uses name-date or content if you choose so). Then I can choose to synchronize (two way) or mirror (one way) or update (idk).

Currently exploring this solution. Will update this post with results.

First Exploration 04-06-25 @14:42 PM:

1. So it turns out, even while using a simple name-date scan, it was able to detect files that were changed (I guess duh for some simple changes)
2. For my use case, since I hoard data without modifying it much, it's pretty good to just use name-date comparisons
3. Update will copy over new files, but will not delete files removed from the source folder (nondestructive)
4. One way will delete files so be careful.
5. You can make a custom rule set other than the provided three by following these instructions in this link. The one thing I'm interested in, is detecting moved files. This might come in handy if I happen to reorganize how I store some files.