Abstract <p>We report an experimental and theoretical study of supercontinuum generation during filamentation of chirped femtosecond optical pulses in compressed nitrogen under tight-focusing conditions. It is shown that the chirping of pulses leads to a decrease in the efficiency of their spectrum broadening with increasing gas pressure. Furthermore, pulses with a negative chirp exhibit a broader supercontinuum than those with equal modulation depth but a positive chirp. The paper also examines the influence of the emission spectrum width on the plasma formation mechanism and, through this, the feedback effect on the spectrum width. It is numerically demonstrated that such a self-consistent approach significantly improves the simulation results and markedly strengthens the quantitative agreement with the experiment, which is attributed to a softer incorporation of plasma effects for broad-spectrum radiation.</p>