  Several topics from the wide field of QCD studies in Deep-inelastic $ep$
Scattering at HERA are addressed. They include QCD analyses of the inclusive
cross section with the determination of $\alpha_s$ and the proton gluon density
from the $F_2$ scaling violations, and the determination of the longitudinal
structure function $F_L$. QCD analyses of inclusive jet and dijet data are also
presented. Finally jet substructure and three-jet production are discussed.
