The XML Format has changed. Entries and Groups now support custom data. This was only supported on the database in KDBX3.1. Also, the settings now have a modifi

The XML Format has changed. Entries and Groups now support custom data. This was only supported on the database in KDBX3.1. Also, the settings now have a modified date which makes synchronising them when merging databases a lot easier. The other changes are done to the binary format as you say. Also to make the file smaller, attachments are now stored compressed "as is" instead of encoding them in base64 and adding them to the XML structure.