What is hey with 3 y?

"Hey" with 3 y's is a slang expression of greeting or acknowledgement used in online or text-based communication. Adding extra y's to "hey" is a way of emphasizing the greeting, and can also denote friendliness or enthusiasm. The practice of adding extra letters to words for emphasis or style is known as leet or l33t speak, and is often associated with internet culture and gaming communities. While the use of "hey" with multiple y's is not grammatically correct, it has become a popular form of informal communication in certain contexts.