  We explore the symmetry structure of Type II Little String Theories and their
T-dualities. We construct these theories both from the bottom-up perspective
starting with seed Superconformal Field Theories, and from the top-down using
F-/M-theory. By exploiting anomaly inflow and unitarity of the LST worldsheet
theory, we derive strong conditions on the possible 6D bulk theories and their
flavor algebras. These constraints continue to apply if gravity is coupled to
the theory. We also study the higher form symmetry structure of these theories
and show how they get exchanged under T-duality. Finally, we comment on
seemingly consistent bottom-up Little String Theories that cannot be
constructed from the top-down approach.
