After a transfer, why does Finder say the Destination and Source differ in size?Updated 9 months ago

Some people who previously used Finder to copy data have a habit of comparing folder sizes to determine if a copy was successful. Besides this being a flawed method as it doesn't show file corruption, it also produces a lot of false positives. For multiple reasons, folders might contain different file amounts or sizes. Possible contributors may include: 

Ingest Pro doesn’t copy hidden system files (e.g. .DS_Store, .Trash, Spotlight, Time Machine files, etc.).  

Transferring files between different file systems (e.g. from ExFAT to APFS) can result in different sizes due to block size differences.  

Some extended file attributes couldn't be transferred during a transfer between different file systems. 

The operating system may create extra attributes on certain files during a transfer.