As of summer 2020, Airbnb set out a strict no-party policy. Now, regardless of actual occupancy, an Airbnb listing may not allow more than 16 people to stay during a reservation.
Additionally, guests must agree to Airbnb’s Community Guidelines when booking their stay. These guidelines include details about what behavior is acceptable, and allow hosts to add their own rules.
Learn more about Airbnb party prevention on their site.