This why you check your backups periodically and replace the bad ones with good copies. If you’re asking how you know what’s good and bad - traditionally and fundamentally, even if many people here dismiss it, the storage already has checksums, that sneaky bitrot when the storage will give you slightly altered data (instead of saying “Error”) are so small that most people would never encounter this. Now of course serious data hoarders would use checksumming file systems, will do extra checksums for any archived data, also all archiving formats or backup formats have their own checksums too, if one would use that instead of dropping the files in the regular file system.

Just click on the link and then look at your drive, you should be able to spot the difference immediately. Does it look as the drive above (helium) or below (air with the characteristic venting hole and everything)?

Let me guess, it’s an air drive (you can tell easily as they look totally different , these are regular Red, well called now “Plus” even if there’s nothing different, but you get the idea, the air is the one with a hole).

How is the disk formatted? If it’s one of Apple’s file systems, yes won’t be seen in Windows (the disk itself will be visible but no “D:” or anything).

I answered in of your many posts (removed and understanbly, you still have 9 of them about this issue, who knows how many removed ones?!!?!) about the first program found by Google on github that would convert these images. What does that do?

You won’t be able to blindly modify a corrupted block so it doesn’t blow up some decompression algorithm in a program where you have only the binary for the program. But with an open source program, first of all it might not crash, and even if it does you’d be able to see the line and edit it to not crash or give up when something isn’t the expected value.

Are you using a Thunderbolt cable? Most random USB-C cables you get with phones (or even basic external SSDs/enclosures) don’t have the required connections.