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 data type converters by creating a C# class that implements the IDataTypeConverter interface. The class can be added to Converge using the following function call in an Umbraco Composer.