Generalised symmetries and string theory

String theory can be used as a powerful tool for constructing and studying interesting quantum field theories, by translating questions in field theory to questions in geometry. It has become clear in the last few years that these quantum field theories can have a very rich spectrum of symmetries, and a natural question is how these symmetries arise in the string theory constructions. I will give a summary of various recent developments in this field, and sketch some open questions.