Abstract In this paper, we unify and improve some of the results Bourgain, Brezis, Mironescu weighted Poincaré–Sobolev estimate by Fabes, Kenig, Serapioni. More precisely, get counterparts Poincaré–Sobolev-type inequality also Hardy type in fractional case under mild natural restrictions. A main feature obtain is fact that keep track behavior constants involved when parameter approaches to $1$....