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[Display omitted] • DFT has been used to study the optic and electronic properties of Cs 2 AgBiX 6 (X = I ; Br ; Cl and F). • The studied compounds exhibit a semiconductor behavior. • The fluorine based perovskite is the least absorbent. • Bromine and Chlorine based perovskites are very interesting for the photovoltaic and optoelectronic. Lead free halide double perovskites are widely studied for their semiconducting behavior which allows them to be used as absorbing materials in solar cells and optoelectronic applications. In this paper, in order to look for perovskite materials with appropriate absorption and band gap, our aim is to study the electronic and optical properties of Cs 2 AgBiX 6 (X = I , Br , Cl and F) by using the density functional theory (DFT) with generalized gradient approximation (GGA). The found results show that the investigated halide compounds present a semiconductor features which absorb in a long wavelength range. Furthermore, iodine based halide perovskite exhibits a negative values of the dielectric function real part which correspond to a high photon reflection, besides the fluorine one is the least absorbent material. From the obtained results, our work confirm that, bromine and chlorine based double perovskites are very interesting for the photovoltaic and optoelectronic applications. [ABSTRACT FROM AUTHOR]