As the healthcare industry continues to evolve digitally, Fast Healthcare Interoperability Resources (FHIR) has emerged as a key standard for exchanging healthcare data. Created by HL7, FHIR simplifies the integration and sharing of electronic health records (EHRs) across various platforms.
While there are numerous commercial offerings, open-source solutions are instrumental in driving FHIR adoption. These community-driven tools and libraries empower developers, researchers, and healthcare professionals to more effectively build, test, and implement FHIR-compliant systems.
In this article, we explore the top open-source FHIR tools and libraries in 2025, categorized for better understanding.
Open Source FHIR Tools and Libraries in 2025
FHIR Servers
1. HAPI FHIR
Language: Java
Repository: GitHub – HAPI-FHIR
Description: HAPI FHIR is a popular open-source framework in Java for working with FHIR. It supports all versions from DSTU2 to R5 and offers a RESTful API, flexible security features, and database support through JPA for storing data.
Use Case: Ideal for building FHIR-compliant backends and integrating with enterprise systems.
2. Microsoft FHIR Server for Azure
Language: C# (.NET Core)
Repository: GitHub – azure/fhir-server
Description: This FHIR server is optimized for use with Microsoft Azure and built for cloud scalability. In addition to supporting FHIR versions R4 and R5, it has sophisticated features like role-based access control (RBAC) for safe data access and SMART on FHIR integration.
Use Case: Cloud-native FHIR applications using Azure services.
3. Firely Server (Formerly Vonk)
Language: .NET
Repository: GitHub – FirelyServer
Description: Firely Server is a lightweight, modular FHIR server that supports R4 and R5, and it was developed by one of the original FHIR creators. It has OAuth2 and validation plugins.
Use Case: Enterprise-grade .NET-based solutions with fine-grained FHIR control.
FHIR Libraries
4. FHIR.js
Language: JavaScript
Repository: GitHub – FHIR.js
Description: A lightweight JavaScript client for FHIR servers. Designed to run in web browsers or Node.js environments.
Use Case: Frontend applications and browser-based FHIR clients.
5. SMART on FHIR Client JS Library
Language: JavaScript
Repository: GitHub – SMART JS Client
Description: A JavaScript library for using OAuth2 to connect apps to SMART on FHIR-compliant systems.
Use Case: Web applications needing secure, authenticated access to FHIR data.
6. FHIR .NET API (Hl7.Fhir.R4)
Language: C#
Repository: GitHub – Firely .NET SDK
Description: The official .NET SDK for HL7 FHIR. It includes parsers, serializers, model classes, and validation tools.
Use Case: Enterprise .NET applications integrating with FHIR APIs.
Testing & Validation Tools
7. Inferno
Language: Ruby
Repository: GitHub – Inferno Framework
Description: ONC created an open-source test suite to confirm certification readiness and FHIR compliance.
Use Case: Compliance testing for ONC Health IT Certification, vendor assurance.
8. Touchstone
Language: Java
Description: Touchstone provides a free, open-access sandbox to test FHIR APIs against a wide range of scenarios, despite it being a commercial product.
Use Case: Comprehensive FHIR server testing with a community of testers.
FHIR Data & Utilities
9. Synthea
Language: Java
Repository: GitHub – Synthea
Description: A synthetic patient generator that generates realistic FHIR datasets for research and development while adhering to PHI regulations.
Use Case: Simulated patient data for testing, research, and training.
10. FHIRPath Evaluator
Language: Various (Node.js, Java, .NET)
Description: Condition evaluation, rule engines, and complex query parsing all benefit from tools for evaluating FHIRPath expressions.
Use Case: Data querying and validation logic in FHIR apps.
FHIR AI/ML Integrations
11. FHIRWorks on AWS
Language: TypeScript / AWS Services
Repository: GitHub – FHIRWorks
Description: AWS Lambda, DynamoDB, and API Gateway were used in the development of this serverless FHIR implementation. incredibly scalable and appropriate for combining workloads related to AI and ML.
Use Case: Cloud-native, AI-powered healthcare applications on AWS.
Quick Reference Table For Open Source FHIR Tools
| Tool/Library | Language | Category | Best For |
|---|---|---|---|
| HAPI FHIR | Java | Server | Custom FHIR APIs and backends |
| Microsoft FHIR Server | C# | Server | Azure-native applications |
| Firely Server | .NET | Server | Enterprise systems with FHIR needs |
| FHIR.js | JavaScript | Client | Web and mobile FHIR apps |
| SMART JS Client | JavaScript | Client | SMART on FHIR app development |
| Hl7.Fhir.R4 (Firely SDK) | C# | SDK | .NET-based systems |
| Inferno | Ruby | Testing | ONC certification and validation |
| Touchstone | Java | Testing | Community and vendor interoperability |
| Synthea | Java | Data Gen | Generating synthetic FHIR data |
| FHIRPath Evaluator | Various | Utility | Rule engines, complex query parsing |
| FHIRWorks on AWS | TypeScript | Serverless | Scalable serverless cloud deployments |
Conclusion
Interoperability is becoming a reality thanks to these open-source tools, and FHIR adoption is speeding up. These tools can offer a strong foundation without the expense of proprietary software, whether you’re a researcher in need of synthetic data, a hospital IT team setting up an FHIR server, or a developer creating a mobile app.
Organizations can create more inventive, scalable, and transparent healthcare solutions by utilizing the power of open source.
