Is mozzarella cheese vegetarian?
In fact, most buffalo mozzarella that I've seen is NOT vegetarian. Rennet, derived from the stomachs of young buffaloes, is required for the curdling process. (The young buffaloes must be killed for their rennet to be extracted.)
You should check the ingredients and do some research on individual brands before buying, because not all cheeses are the same. Many mozzarella cheeses are made using vegetable, microbial, or other vegetarian-safe rennet or rennet substitute.