The Brown-York stress tensor provides a means for defining quasilocal gravitational charges in subregions bounded by a timelike hypersurface. I will discuss the generalization of this stress tensor to null hypersurfaces. Such a stress tensor can be derived from the on-shell subregion action of general relativity associated with a Dirichlet variational principle, which fixes an induced Carroll structure on the null boundary. The stress tensor can be shown to satisfy a covariant conservation equation as a result of the gravitational constraint equations on the null surface. For transformations that act covariantly on the null boundary, the Brown-York charges coincide with canonical charges constructed from the Wald-Zoupas procedure, while for anomalous transformations, the charges differ by an intrinsic functional of the boundary geometry. I will comment on some possible applications of the null Brown-York stress tensor to symmetries of asymptotically flat spacetimes and celestial holography.
