The effect of K2O on silicate structural units in soda lime silicate glasses is investigated. The structural, optical, and mechanical properties of 64SiO2-16Na2O-12CaO-2Al2O3−(6−x)MgO-xK2O (x=2, 4, and 6), where the constituents are given in mole percent, are reported. The physical parameters exhibit significant variation on the addition of K2O in place of MgO in the glass. The amorphous nature of the samples is confirmed by X-ray diffraction patterns. Fourier transform infrared spectroscopy and Raman spectroscopy confirmed the structural changes on the addition of K2O in place of MgO. The optical properties of the prepared samples were studied by diffuse reflectance spectroscopy. The microhardness and the fracture toughness were determined by the Vickers hardness test. These results pave the way for effectively utilizing the present glasses for applications in automobile windshield glasses. The transmittance of all the glasses is higher than 85% and constant throughout the visible region and the hardness is comparable to that of commercial windshield glasses.