Hong kong to shanghai is an international or domestic flight baggage allowance?

it is an international flight.

Thanks judy, is there any site stating this?
I would like it to be an international flight for a bigger baggage allowance but
further searching I found it listed as domestic destinations at other site.
Though, I couldn't find it stated explicitly on the official sites of "china eastern" and "HK" airlines. Thanks a lot

The flights from mainland China to HK are handled as international flights. It's the rule. If you have any doubt, further confirm with your airline company.

Thanks a lot Chang :D