Top: spectrum of a model galaxy with various f_esc. The model galaxy is at z = 6 and has a mass of M_* = 10⁹ M_⊙, metallicity of Z = 0.05 Z_⊙, ionization parameter of log U = −2, constant star formation switched on at 5 Myr, and dust modelled via the Calzetti (Calzetti et al. 2000) dust curve with A_v = 0.2. As f_esc increases, the β_UV slope becomes steeper due to reduced nebular continuum emission, and the emission lines become weaker. The continuum emission is also affected as its nebular component scales with f_esc. The full spectrum thus contains information on the escape fractions, which we exploited to constrain the f_esc of galaxies with NIRSpec spectra. Bottom left: zoomed-in view of Hα. Bottom right: zoomed-in view of Hβ+[O III].