Converge has been designed to allow the transfer of content between different versions of Umbraco. A number of built-in data type converters are supplied to transform legacy data types to their updated versions before the comparison is made, so that the content is upgraded during the process. For example, from Umbraco version 7.12.0 onwards Tags can be stored as JSON rather than CSV. A built-in converter will convert the CSV Tags to JSON during the comparison and merge.
You can also add your own converters by creating C# classes that implement Converge interfaces. The classes can be added to Converge using an Umbraco Composer, for example: