The two signs that actually decide it
Forget size, head shape and temperament — breeders' folklore offers plenty of guesses, but leopard gecko sex is read from one place: the underside of the tail base. A male carries a distinct V-shaped row of preanal pores across the skin just in front of the vent, visible as a line of small darkened dots, often with a waxy secretion in a mature animal. Behind the vent, the male also shows two separate bulges side by side, the pockets housing the hemipenes, giving the tail base a noticeably paired, swollen look from below and from the side. A female has neither feature in developed form: her pore row is faint and flat, and her tail base runs smooth and single into the tail.
How to look without upsetting the gecko
The kindest method is to avoid turning the gecko over by hand at all. Let it walk onto a clear plastic tub or a piece of glass, lift the container, and look up from beneath with a phone torch; the pores and bulges show clearly through the base and the gecko stays calm and supported. A magnifier or a zoomed phone photograph helps with young animals, and taking that photograph gives you a record to compare against in a month's time. Keep the session brief, support the whole body if you do hold the gecko, and never squeeze or force the tail upward — a leopard gecko can drop its tail under rough handling, and no identification is worth that.
Why young geckos fool everyone
In the first months of life the male equipment simply has not developed enough to read. Juvenile males show pores so faint they pass for female, and the paired bulges emerge gradually rather than on a single day. This is why geckos sold as one sex so often surprise their owners later, and why incubation temperature, which influences sex in this species, still does not let you sex the hatchling in your hand. The practical timeline most keepers work to: tentative guesses from around three to four months, growing confidence after that, and a verdict worth trusting at about six months, by which point a male's pores are dark, distinct and unmistakable. Until then, label the gecko unsexed in your records rather than writing down a hope.
Why the answer changes how you house it
Sexing is not trivia, because it decides the housing plan. Two males housed together will fight as they mature, sometimes suddenly after months of apparent peace, and a male kept with a female will breed her whether or not you want eggs, which carries real risks for a young female. So an unreliable early verdict should never be the basis for pairing youngsters; keep juveniles singly or be ready to separate the moment the six-month check clarifies things. Once the sex is certain, write it into the gecko's permanent details: its KinsLe Pet Pass carries that identity alongside its owner contact information, so the confirmed sex travels with the gecko to shows, sitters and any future home instead of being rediscovered by each new keeper.