You're on the sofa. A friend sits down and your dog goes rigid, placing themselves between you. A growl follows. It can feel flattering to call this protection, but a growl tells you someone needs more space. The reason may involve fear, guarding access to you, or discomfort. You cannot settle that from one scene.
For now, avoid the setup that leads to a warning. Give your dog a comfortable resting place away from close greetings, use a gate or separate room before visitors arrive. Ask people not to pet, lean over, or step around the dog to reach you. Keep children and visitors safely apart from a dog who has growled or snapped. Do not punish the growl, push the dog off you, or have a friend repeat the approach to "prove" it is fine.
Make the pattern clear to a professional
Note exactly when it happens: on the sofa, near a doorway, when one person hugs another, or when someone reaches for you. Include body language before the growl and whether the dog can move away. Share this with your veterinarian, especially if the behavior is new, pain and illness can lower tolerance. If there has been a snap, bite, or repeated guarding, seek a qualified, reward-based behavior professional for an individual safety plan.
While you arrange help, teach simple movement cues away from visitors: reward the dog for going to their bed when the room is quiet, then gently add ordinary movement at a distance. This is not a license to practice close approaches that have caused growling. A safe household plan comes first.
A dog who can rest while people greet each other is doing enough. They do not need the job of deciding who may come close to you. For more on guarding around people, see the resource-guarding guide, no visitor should be used to test whether the dog can tolerate an approach
Sources: Dogs Trust: Resource guarding in dogs. Dogs Trust: Dog aggression towards visitors.