The Basis Set Exchange (BSE) is a quintessential service for the quantum chemistry community. First online in 2007, it is well known by both users and basis set creators as the go-to source for basis sets. The current version of the BSE has been developed using modern software design and best practices, and was released in 2019. The basis set data is managed by a stand-alone Python library with command-line tools and an accessible programming interface. The web site preserves the general layout and workflows of the earlier versions of BSE, while using up-to-date web development libraries and adding helpful features requested by the user community. The modular design increases adaptability of the project and ensures its long-term viability.