A Blacklight developer is responsible for creating, implementing, and maintaining software applications using the Blacklight framework, a free and open-source Ruby on Rails plugin. This framework is designed for creating library user interfaces and discovery environments. The developer works with Solr, an open-source search platform, to index and search data. They customize the user interface, improve search functionality, manage metadata and ensure the application meets user needs and expectations. Blacklight developers also troubleshoot issues, provide technical support, and stay updated on the latest industry trends and technologies to enhance the functionality and user experience of the application.