CIMPL (pronounced “simple”) is a domain-specific language for defining clinical information models and providing consistent information content across multiple domains and multiple FHIR versions. CIMPL provides a compact description of clinical data that can be directly translated into FHIR profiles and FHIR implementation guides. CIMPL is edited as text; this allows for excellent version control, branching and merging using conventional source code control tools such as Github. Along with CIMPL the language, we have created an integrated open-source ecosystem that supports multiple textual, hierarchical and graphical representation of the profiles, as well as exports of those profiles as Javascript classes and schemas.