The definition of angular momentum at null infinity has been a subtle issue since the 1960’s, due to the discovery of "supertranslations". Supertranlations are ubiquitous in any description of null infinity and independent of the underlying spacetime. However, in presence of gravitational radiation, the classical definition of angular momentum can be shifted away by supertranslations and thus not well-defined. In this talk, I shall show how the theory of quasilocal angular momentum and optimal isometric embeddings identifies a correction term, and leads to a new definition of angular momentum that is free from any supertranslation ambiguity. This is based on joint work with Po-Ning Chen, Jordan Keller, Ye-Kai Wang, and Shing-Tung Yau.