About Vonk

Professional FHIR Server

Vonk is an enterprise-grade FHIR Server meant for production environments large and small alike. Vonk is designed and built from the ground up, using our extensive experience with the FHIR specification, Microsoft .Net programming and Vonk’s predecessor Spark. We have a free edition for testing and educational purposes and a licensed version with support.

There is always a Vonk that fits your needs

Vonk is available in different distributions. Vonk FHIR Server is an integrated, turn-key FHIR server that runs on its own storage. Vonk FHIR Facade enables you to open up legacy systems to the FHIR ecosystem, leaving the FHIR heavy lifting to us. Vonk FHIR Components (“Build Your Own FHIR Server”) is a set of NuGet packages that allows you to build a highly customized version of Vonk, or integrate FHIR Server operations in your own application.

Try it

You can try Vonk FHIR Server in different ways. Visit https://vonk.fire.ly to access the public FHIR endpoint hosted by Vonk. Or go to http://docs.simplifier.net/vonk to see how you can download and run your own Vonk FHIR Server for evaluation.

  • The Vonk server is a valuable component of our EHR, why reinvent the wheel when you can have the experts do it for you? FHIR implementation of our EHR was a breeze thanks to the Vonk Server and the insights of Firely.


    NeoDeck Holdings – Puerto Rico

  • Hook MD revolutionizes the way a doctor has access to all relevant patient data, regardless of the source. Interoperability is a key selling point for us. That’s why we chose Vonk as our app back-end, and the FHIR consultants of Firely to help our team build the solution.

    CEO Hook MD

    New York, United States

  • We chose Vonk FHIR Server as a solution for the management of digitized medical records. To integrate VONK with our existing document storage, we needed two specialized plugins. In a one day hands-on workshop we did not only learn how to build a Vonk plugin, we even prototyped our solution!


    Gefyra GmbH – Germany


No matter which distribution of Vonk you intend to use, it comes with a pack of features. Most of these features refer to operations in the FHIR RESTful API as defined in the FHIR Specification. Vonk implements FHIR version STU3, in both JSON and XML formats. It can handle all resource types, including profiled resources, except for Binary. The current beta version already supports most of the interactions.

Features include:

  • capability statement (metadata)
  • read, create, update, delete
  • search on all searchparameters defined in the specification
    • chained parameters and choices
    • search on multiple resource types (“_type”)
    • _include
    • unification of quantities
  • history (instance, type & system)
  • batch and transaction (only on a database engine that supports transactions)
  • validation of a resource against the core specification or a custom profile
  • snapshot generation
  • extensible with custom operations (“$<your-operation>”)
  • support for several more options, e.g. _summary, _elements
  • custom search parameters
  • subscriptions
  • compartment search
  • terminology operations

More features are on their way. Priority is volatile and can be influenced by customer requests. Features on the roadmap include:

  • documents ($document)
  • resource type ‘Binary’


Vonk can run natively on SQL Server, SQLite, MongoDB, CosmosDb and an in-memory storage. Support for other database engines can easily be added on request. Vonk FHIR Facade and Vonk Components allow you to connect Vonk to existing databases.


  • Authentication with an OAuth token against a separate OAuth identity provider
  • Authorization based on Smart-on-FHIR scopes and launch context
  • Extensible system for adding custom authorization or scoping of a request to a subset of the data
  • Https support


There is a wide variety of deployment options for Vonk.

  • Binaries with a very simple installation procedure
  • Docker images
  • Azure App Service
  • Cross platform (Windows, Linux, OS-X)
  • Flexible logging
  • Can be connected to Microsoft Application Insights
  • Add profiles, or restrict to specific profiles
  • Add or restrict the search parameters
  • Enable or disable operations

Technical details

Vonk FHIR Server is built with Microsoft ASP.Net Core, which enables cross-platform support and fully self-contained binaries (no pre-installed .Net Framework required). It runs on Kestrel, a very fast web server that is highly integrated with ASP.Net Core. And of course, it utilizes our own HL7.Fhir API.

What happens to Spark?

This is up to the community. Firely has put a lot of effort in Spark and provides all of this effort to the community. It’s open source, available on GitHub. But Firely will neither port Spark to STU3 nor provide support for DSTU2.