Decomposition results of a sample of synthetic spectra with two identical Gaussian components, whose S/N, peak separation and FWHM parameter were varied. Blue and black lines indicate the results obtained for the decomposition runs with GAUSSPY+ and GAUSSPY, respectively. Left: Percentage of fitted spectra with two Gaussian components as a function of peak separation for S/N <  5 (dashed lines) and ≥5 (solid lines). The dotted vertical line indicates the separation threshold for two identical Gaussian components without noise. Right: Percentage of fitted spectra with two Gaussian components as a function of their S/N for peak separations of < 3 × σ_i (dashed lines) and ≥3 × σ_i (solid lines).