<p>In this article, the optoelectronic and structural properties of lead-free halide double perovskite (HDPs) Cs₂AgM³⁺X₆ (M³⁺  = Sb, Bi; X = Cl, Br, I) were calculated using density functional theory (DFT) approximations. The structural analysis of Cs₂AgSbX₆ and Cs₂AgBiX₆ (X = Cl, Br, and I) indicates that the lattice constant and unit cell volume increase progressively with the increase in halides. The electronic properties reveal that all these semiconductors are good absorbers of incoming photons at the range of bandgap energy. The bandgap energies of Cs₂AgSbCl₆, Cs₂AgSbBr₆, Cs₂AgSbI₆, Cs₂AgBiCl₆, Cs₂AgBiBr₆, and Cs₂AgBiI₆ are 2.50&#xa0;eV, 1.75&#xa0;eV, 0.98&#xa0;eV, 2.70&#xa0;eV, 2.18&#xa0;eV, and 1.35&#xa0;eV, respectively, lying in the visible range of electromagnetic spectrum, and their electronic bandgaps decrease down the halide group. The compounds with bandgaps in the range of 1.3–1.75&#xa0;eV (Cs₂AgBiI₆ and Cs₂AgSbBr₆) are suitable for solar cell applications, while the compounds with greater bandgaps are good for light-emitting diodes. Halides exhibit covalent bonding with Ag and M³⁺, where the bonding nature is ionic for Cs-Ag, Cs-Bi, Cs-Sb, and Cs-X. The optical properties show that, due to their suitable bandgaps, these HDPs are good absorbers of photons and most desirable for optoelectronic and photovoltaic applications. The critical energy of Cs₂AgSbX₆ and Cs₂AgBiX₆ decreases with the increase in halides from Cl to I. From the refractive index it is clear that these materials are super-luminescent for ultraviolet photons. The oscillator strength shows that transitions occur when the energy reaches the bandgap energy and the number of electrons increases rapidly up to 17&#xa0;eV, after which the oscillator strength saturates at 30&#xa0;eV.</p>