  High-energy jets offer rich opportunities to study quantum chromodynamics,
from investigating the limits of perturbative calculability to constraining the
emergent properties of the quark-gluon plasma (QGP). In these proceedings, we
present new measurements of the fragmentation properties of jets. We report
distributions of the sub-jet momentum fraction $z_r$ measured in pp and Pb-Pb
collisions with ALICE at the Large Hadron Collider. These measurements serve as
input to test the universality of jet fragmentation in the QGP, and offer a
path to elucidate jet quenching effects in the large-$z$ region.
