In this current work, CuO–SnO2: F mixed oxide thin films were synthesized by spray pyrolysis technique on glass substrates. The structural and optical properties were optimized and improved by varying the substrate temperature from 300 to 350 °C by a step of 25 °C. By increasing the substrate temperature, in addition to the CuO monoclinic phase we notice the appearance of the SnO2: F tetragonal phase in the XRD spectrum. Therefore, CuO–SnO2: F coupled oxide thin film, where the ratio in the spray solution (r=3) was successfully grown at the elevated temperature equals to 350 °C. This result was confirmed by Raman and FTIR analyses. SEM analysis of CuO–SnO2: F films elaborated at a substrate temperature equal to 350 °C endorsed the particle-like spherical shape structure with smooth surface. While EDS and Elemental mapping confirmed the presence of the expected elements. By using the transmission reflection spectra, we estimated the values of the refractive index n, the extinction coefficient k and the dielectric constant. In the visible area the refractive index (n) varies from 1.5 to 2.3 and the extinction coefficient k decreases from 0.8 for Ts = 300 °C, up to about 0.2 for Ts = 350 °C. Moreover, the photoluminescence spectra of the films was investigated and interpreted. The gas-sensing measurements revealed that CuO–SnO2: F thin films grown by spray-pyrolysis method at the substrate temperature equals to 350 °C, can detect minuscule traces of O3 gas (30 ppb) with good sensitivity, fast response and recovery times (60 s and 79 s respectively), at relatively low temperature (200 °C). This manuscript reports the effectiveness of our homemade device as promoter ozone gas sensor in many industrial applications.