The Two Landmarks That Answer the Question
You tell a young Basset Hound's sex from two landmarks: the belly and the area under the tail. Roll the puppy gently onto its back in your lap, fully supported, or have someone hold the puppy standing while you look underneath. A male puppy has a small, soft sheath on the underside of the belly, set noticeably forward, roughly midway between the hind legs and the ribs, with a tiny opening at its tip. His rear opening sits separately below the tail, so a male shows one feature on the belly and one under the tail, well apart from each other.
A female puppy has a smooth belly with no sheath at all. Her second opening sits directly below the rear opening, very close under the tail, so both features are neighbours in the same small area. That distance is the clearest test at any age: features far apart mean male, features close together under the tail mean female. On a Basset puppy, the breed's loose skin and low, heavy build can hide things in folds, so use good light, part the belly fur gently, and look rather than guessing from a quick glance.
Why Basset Puppies Are Easy to Get Wrong
Young puppies of any breed have small, undeveloped anatomy, but a Basset Hound adds its own difficulties. The belly hangs low, the skin is abundant, and the umbilical cord stump on a very young puppy sits close to where a male's sheath will be, which is the classic source of confusion: a healing cord stump is centred on the midline and shrinks and dries over the first days, while a male's sheath is a soft, permanent structure slightly further back with a defined opening. If what you are looking at is drying and changing daily, it is the cord, not an answer.
The anatomy check above, done calmly with the puppy warm and supported, is the only home method worth trusting, and even experienced breeders occasionally recheck a puppy they sexed in a hurry.
Comparing Littermates Makes It Obvious
If the litter is together, comparison is your best tool. Place two Basset puppies side by side on their backs in turn, and the difference usually becomes plain within seconds: one has the belly feature and a clear gap before the tail, the other has a plain belly and everything gathered under the tail. Sexing a single puppy alone, with nothing to compare, is where most mistakes happen, especially in the first couple of weeks when everything is tiny.
Handle the puppies briefly and gently for this job. If the breeder has already sexed and marked the litter, verify politely anyway if the choice of puppy depends on it; mistakes discovered at home, after bonding and naming, are awkward for everyone, and a good breeder would rather recheck at the visit than correct a mix-up later.
Getting It Confirmed and Recorded
Have the sex confirmed at the puppy's first veterinary check and recorded on the health record, because that record follows the puppy into everything else: future appointments, boarding paperwork, and the details a new owner receives at handover. If you are choosing between a male and a female Basset, base the decision on the life you are planning (a male Basset is typically a little larger and heavier at maturity, and the sexes differ in the neutering conversations you will have with your veterinarian) rather than on claims about one sex being easier, since individual temperament varies far more than sex does in this breed.
For the moments in between, KinsLe's Kinny can talk you through the belly and tail landmarks again while the puppy is in front of you, with what you confirm kept alongside the puppy's profile.