Evolution of the compactness parameter for the full grid of single (blue) and binary binary-stripped (red) models as a function of initial mass (left) and reference core mass (right). From top to bottom: we show the compactness at the moment of core helium depletion (D, top), core oxygen depletion (F, middle), and the onset of core collapse (G, bottom). For the models at the onset of core collapse, open symbols indicate models that have experienced shell mergers. For every phase of the evolution, we indicate the range of changes in the compactness parameter with blue and red shaded regions. The upper bound of this region corresponds to the compactness evaluated at m = 2 M_⊙ and the lower bound to the compactness evaluated at m = 3 M_⊙. Trends in the compactness parameter as a function of mass are consistent between different definitions of the compactness for the range considered. The reference core mass is defined as the mass of the helium core at the moment of core helium depletion.