The present work investigates the effect of initial conditions on the induction length (Δi) of hydrogen–air detonations using ZND computations and detailed chemistry. Additionally, sensitivity analyses were performed across a wide range of conditions to gain deeper insights into the role of chemical kinetics in influencing the detonation structure. The impact of H2O addition as a diluent on ∆i of hydrogen–air mixtures was also analyzed. The results reveal that increasing the initial temperature leads to a reduction in the induction length of lean H2–air detonations. Meanwhile, the induction length increases for stoichiometric mixtures. Also, under low-pressure and low-temperature conditions, Δi decreases monotonically. In the low-temperature zone, chain-branching reactions like H + O2 ↔ O + OH and H2 + O ↔ H + OH exhibit negative sensitivity coefficients. The magnitude of these negative sensitivity coefficients decreases with increasing equivalence ratio at a constant initial temperature and pressure. However, at elevated temperatures, the effect of these chain-branching reactions becomes minimal. The addition of H2O to the hydrogen–air mixtures significantly increases the induction length. Sensitivity analysis revealed that the sensitivity coefficients of the dominant chain-branching reactions became increasingly negative with higher levels of H2O dilution. However, in undiluted mixtures, the sensitivity coefficients of these reactions were relatively small.