Libraries need to adapt in reaction to Plan S, not only by supporting and advising their researchers, but by looking at their role in the field of scholarly communication. To achieve this, libraries must look at scholarly owned and library-owned infrastructure. To counter the non-sustainable APC model, they will have to invest in open infrastructure to build and modernize their services and coordinate with other key players. And lastly, they will have to make sure that their platforms, especially journal platforms and repositories, are compliant with the organisational and technical requirements of Plan S.