The main difference between the words Aunty and Auntie are two, the first one is that Aunty is more frequently used in British English while Auntie is more frequently used in American English. The other is that Aunty is mostly used in a more formal tone while Auntie is considered a less formal word. The term Aunty can be defined in two different ways, the first one being that an aunty is a sister of either your father or mother, it can also be called to someone who is the wife of your uncle. The second definition will be that which is not related to anyone. It should be noted that most of the people use the same word for their grandparent which are then called grand-aunt.
Auntie | Definition of Auntie by Oxford Dictionary on spangangoras.com also meaning of Auntie
Both are accepted by Oxford English dictionary, Collins dictionary and others. They are just two alternatives of the same meaning. I used to write Aunty so Aunty is correct spell. Well both are right.
You would have heard people calling their mother, mom or mama, very similarly aunty and auntie are the two words people use for their aunt. Relations are all based on affection and understanding, while showing off these essence one uses informal words. Following it, aunt is the formal word and when one refers or call their aunt in informal way it becomes aunty or auntie. Here it should be kept mentioned that words like bro or broda, are the informal words used in place of brother.