Jania longifurca is a seaweed with an erect, bushy thallus and a crustose base. Its size ranges from 3 to 7 cm high, and its color from violet to grey, in a living specimen, and from violet to yellow white ivory when dried. It presents dichotomous and regular branching, and a cylindrical, slightly compressed intergenicula, becoming broader at the insertions of lateral branches. It can either have an epilithic habitat, often present in the same sites as Jania rubens, or epiphytic on Cystoseira species. Jania longifurca can be found from the surface to 20 m deep, and from May to June.