Firely .NET SDK
The open-source FHIR library for .NET developers. FHIR R5, R4, R4B and STU3. Actively maintained by the team that helped build the standard.
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Everything you need to work with FHIR in .NET
The Firely .NET SDK gives you parsing, serialization, validation, profiling, RESTful API calls, and FHIRPath — all in one open-source library. Used by hundreds of healthcare teams worldwide and actively maintained by the team that helped build the FHIR standard.
Install the latest version
dotnet add package Hl7.Fhir.R5Or choose your FHIR version
What’s included
RESTful API
Connect to any FHIR server and retrieve, create, update, or delete resources using standard HTTP.
FHIR data model
Work with FHIR resources as strongly-typed .NET objects — no manual parsing, no guesswork.
Serialization
Serialize and deserialize FHIR resources to JSON and XML — in and out, without friction.
Profiling
Create and apply FHIR profiles with the built-in SnapshotGenerator. Validate against custom constraints.
Multi-version support
Full support for R5, R4, R4B, and STU3 — build once, stay compatible as the standard evolves.
FHIRPath
Run complex queries and transformations on FHIR resources using FHIRPath — directly in your .NET code.
Need more? Three additional libraries available on NuGet.
Available separately – install only what you need.
CQL Engine
Execute CQL and evaluate CQL logic in libraries on the .NET platform. Created with NCQA, tested against HEDIS measures.
FHIR Packages
Manage FHIR resources and organize them into logical groups and versions for easier management and sharing.
Validation
Out-of-the-box FHIR validation for syntactical and semantical correctness — drop it into your pipeline.
Need help getting started?
Learn from the team that built the standard
Hands-on training for developers and health IT professionals.
Ready to start? Install the Firely .NET SDK now.
Available for FHIR R5, R4, R4B and STU3 via NuGet.