Estimated geometric albedo of WASP-18 b based on the retrieval results in comparison to the passbands of CHEOPS and TESS. The green line shows the geometric albedo with an H⁻ abundance derived by assuming chemical equilibrium (extremely low A_g values, reaching 0.03 at short wavelengths). For the purple line, this abundance is artificially reduced by 98% (yielding A_g values comparable to our results in the CHEOPS and TESS passbands), while for the yellow case the H⁻ continuum is entirely removed as an opacity source. We further explored the effect of removing TiO and VO (red) as well as Na and K (blue). The impact of the former is negligible and the red curve lies hidden behind the yellow model. The latter reveals however more significant scattering spectral features, especially in the CHEOPS and TESS passbands. The strong increase of A_g towards lower wavelengths is caused by the λ⁻⁴-dependence of Rayleigh scattering.