  We derive an action describing edge dynamics on interfaces for gauge theories
(Maxwell and Yang-Mills) using the path integral. The canonical structure of
the edge theory is deduced and the thermal partition function calculated. We
test the edge action in several applications. For Maxwell in Rindler space, we
recover earlier results, now embedded in a dynamical canonical framework. A
second application is 2d Yang-Mills theory where the boundary action becomes
just the particle-on-a-group action. Correlators of boundary-anchored Wilson
lines in 2d Yang-Mills are matched with, and identified as correlators of
bilocal operators in the particle-on-a-group edge model.
