At its core growling is about communication writes, Stephanie Gibeault, MSc, CPDT. It is a warning, a symptom of your puppy’s discomfort. Rarely an indication of aggression initially, growling at strangers is a sign that something is wrong. The most likely explanation is the puppy is fearful of people they don’t know.
Source: AKC, January 19, 2021. Link. Whenever your puppy is interacting with someone, be sure to instruct the person how to properly approach. Don’t allow them to loom over your puppy or stare into their eyes as those are threatening behaviors that may increase your pup’s discomfort. Instead, have the person kneel and turn sideways, holding out their fist for the puppy to smell.