Lantern is an open source tool for monitoring fielded health IT systems' certified FHIR API endpoints. It gathers availability information and information about FHIR support from endpoints' capability statements and provides visualizations to show FHIR adoption and patient data availability across the nation. Lantern helps to ensure that patients will have digital access to their data by providing visibility into levels of FHIR adoption as well as FHIR endpoint availability and usability.