Glossary
What is FHIR R4 vs R5?
FHIR R4 (2019) is the version most production deployments and regulators reference; FHIR R5 (2023) adds new resource types, refined search semantics, and the topic-based subscription model.
In context
R4 is the practical FHIR baseline. US regulators (CMS, ONC) reference R4; European regulators (EHDS, MDR) reference R4; most EHRs expose R4 surfaces. R4 conformance is a hard requirement for interoperability with the existing healthcare ecosystem.
R5 is forward-looking. New deployments that anticipate R5-specific use cases (genomic data with GenomicStudy, structured topic-based subscriptions) consider R5 from the start. Most existing deployments stay on R4 and migrate selectively.
How Fire Arrow handles it
Fire Arrow targets FHIR R4 as the primary supported version. Migration paths to R5 will be evaluated as the regulatory and integration landscape moves toward it.