  The program HDECAY determines the partial decay widths and branching ratios
of the Higgs bosons within the Standard Model with three and four generations
of fermions, including the case when the Higgs couplings are rescaled, a
general two--Higgs doublet model where the Higgs sector is extended and
incorporates five physical states and its most studied incarnation, the minimal
supersymmetric Standard Model (MSSM). The program addresses all decay channels
including the dominant higher-order effects such as radiative corrections and
multi-body channels. Since the first launch of the program, more than twenty
years ago, important aspects and new ingredients have been incorporated. In
this update of the program description, some of the developments are summarized
while others are discussed in some detail.
