HAPI FHIR Test Server API

Free public HAPI FHIR R4 test server with no key: query Patient, Observation, Condition and every other FHIR resource against synthetic data. For development and learning only.

No API key requiredCORS enabledHTTPSFree tier

Endpoint tested and returned HTTP 200 on 2026-08-21

What is the HAPI FHIR Test Server API?

The HAPI FHIR public test server is a free, key-free FHIR R4 endpoint hosting synthetic healthcare data. It implements the full FHIR REST API — search, read, history and capability statements — so developers can build and test FHIR clients without provisioning a server or handling real patient data.

Learning FHIR is difficult without a server to talk to, and provisioning one is a substantial task in itself. This public instance removes that barrier: it speaks standard FHIR R4, so `GET /baseR4/Patient?_count=1` returns a proper searchset Bundle with paging links, exactly as a production server would. The data is synthetic, much of it generated by tools such as Synthea, and the example's patient is transparently named `Synthetic Patient SYN-000004`.

Treat it strictly as a sandbox. Anyone can write to it, records are periodically purged, and availability is best-effort — the same properties that make it convenient make it unsuitable for anything real. Critically, never post actual patient data: the server is world-readable, so writing identifiable information to it is a data breach in the most straightforward sense. The Bundle structure is worth studying while you are here, since `type: searchset`, the `link` array with its `next` relation, and the `entry[].search.mode` field distinguishing matched from included resources are the mechanics every FHIR client must handle.

Quick facts

Base URL: https://hapi.fhir.org/baseR4
Authentication: No API key or account — the server is deliberately open, including for writes. That openness is precisely why it must never receive real patient data. HAPI FHIR itself is open source under Apache 2.0.
Rate limit: No published limit, but this is a free community server with no availability guarantee and periodic data purges. Do not build anything that depends on it.
Pricing: Free. Run your own HAPI FHIR instance for anything beyond experimentation.
CORS: Enabled — callable directly from browser JavaScript
Official docs: Read the docs

How to use the HAPI FHIR Test Server API

Every request below was executed against the live API on 2026-08-21, and the response shown is the real body it returned — not an illustration.

1. Search for a patient resource and inspect the Bundle

GET https://hapi.fhir.org/baseR4/Patient?_count=1

curl

curl 'https://hapi.fhir.org/baseR4/Patient?_count=1' \
  -H 'Accept: application/fhir+json'

JavaScript (fetch)

const res = await fetch("https://hapi.fhir.org/baseR4/Patient?_count=1", {
  headers: {
    "Accept": "application/fhir+json",
  },
});
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);

Python (requests)

import requests

headers = {
    "Accept": "application/fhir+json",
}

res = requests.get("https://hapi.fhir.org/baseR4/Patient?_count=1", headers=headers, timeout=20)
res.raise_for_status()
print(res.json())

Response — HTTP 200

{
  "resourceType": "Bundle",
  "id": "31725add-83b8-4c5a-8e55-1715feb914e1",
  "meta": {
    "lastUpdated": "2026-08-21T03:41:54.173-04:00"
  },
  "type": "searchset",
  "link": [
    {
      "relation": "self",
      "url": "https://hapi.fhir.org/baseR4/Patient?_count=1"
    },
    {
      "relation": "next",
      "url": "https://hapi.fhir.org/baseR4?_getpages=31725add-83b8-4c5a-8e55-1715feb914e1&_getpagesoffset=1&_count=1&_pretty=true&_bundletype=searchset"
    }
  ],
  "entry": [
    {
      "fullUrl": "https://hapi.fhir.org/baseR4/Patient/sindhu-syn-000004",
      "resource": {
        "resourceType": "Patient",
        "id": "sindhu-syn-000004",
        "meta": {
          "versionId": "6",
          "lastUpdated": "2026-07-31T02:45:12.904-04:00",
          "source": "#C75WT8HzGJLAXRKr",
          "tag": [
            {
              "system": "https://sindhu-ecrf.local/tags",
              "code": "sindhu-synthetic-40"
            }
          ]
        },
        "identifier": [
          {
            "system": "https://sindhu-ecrf.local/synthetic-patient-id",
            "value": "SYN-000004"
          }
        ],
        "active": true,
        "name": [
          {
            "text": "Synthetic Patient SYN-000004",
            "family": "SYN-000004",
            "given": [
              "Synthetic"
            ]
          }
        ],
        "gender": "male",
        "birthDate": "1952-01-01"
      },
      "search": {
        "mode": "match"
      }
    }
  ]
}

Parameters

Parameter	Type	Required	Description
`(resource type)`	path segment	Required	Any FHIR R4 resource: `Patient`, `Observation`, `Condition`, `Encounter`, `Medication` and the rest. `Patient`
`_count`	query	Optional	Page size for a search. The server caps it regardless of what you ask for. `1`
`_id`	query	Optional	Search by resource logical id. `sindhu-syn-000004`
`_lastUpdated`	query	Optional	Filter by modification time with FHIR prefixes such as `gt` and `lt`. `gt2026-01-01`
`_include / _revinclude`	query	Optional	Pull in referenced or referencing resources within the same Bundle. `Observation:patient`
`_format`	query	Optional	`json` or `xml`. Content negotiation via the Accept header also works. `json`
`(endpoint) /metadata`	path	Optional	The CapabilityStatement describing everything this server supports. `/baseR4/metadata`

Response fields

resourceTypestring: `Bundle` for search results. Every FHIR response identifies its own type this way.
typestring: `searchset` for a search. Other operations return `batch-response`, `history` and so on.
totalinteger: Total matches when the server computes it — not always present on large result sets.
link[]array: Paging links. Follow the entry whose `relation` is `next`; never construct paging URLs yourself.
entry[].fullUrlstring: Absolute URL of the resource, which is how you address it individually.
entry[].resourceobject: The resource itself, with its own `resourceType`, `id` and `meta`.
entry[].resource.meta.versionId / lastUpdatedstring: Version and modification time. FHIR resources are versioned and the history is retrievable.
entry[].search.modestring: `match` for resources meeting your criteria, `include` for ones pulled in by `_include`. Filtering on this matters when using includes.

What you can build with the HAPI FHIR Test Server API

Develop and test a FHIR client without provisioning a server
Learn FHIR search syntax and Bundle structure interactively
Prototype a healthcare integration before connecting to a real system
Validate that your FHIR resources conform before deployment
Demonstrate FHIR concepts in training material

Common errors and how to fix them

Data has disappeared

The test server is purged periodically.

Fix: Never rely on anything you wrote persisting. Recreate fixtures at the start of each test run, or run your own HAPI instance.

404 on a resource type

Not every FHIR resource is enabled.

Fix: Fetch `/baseR4/metadata` and read the CapabilityStatement. It is the authoritative list of what this server supports.

Search parameter ignored

FHIR search parameters are resource-specific.

Fix: Check the CapabilityStatement for the parameters that resource supports. Unknown parameters may be silently ignored rather than rejected.

Slow or unavailable

It is a free shared community server.

Fix: Expect variable performance and outages. Anything that matters should run against your own instance.

HAPI FHIR Test Server API — frequently asked questions

Is the HAPI FHIR test server free?

Yes, completely free with no key or account, and HAPI FHIR itself is open source under Apache 2.0. It is a community service with no uptime guarantee and periodic data purges.

Can I put real patient data on it?

Absolutely not. The server is world-readable and world-writable, so uploading identifiable patient information would expose it publicly and constitute a data breach. Everything on it should be synthetic.

What is FHIR?

Fast Healthcare Interoperability Resources, the HL7 standard for exchanging healthcare data over a REST API with JSON or XML payloads. It defines both the resource models — Patient, Observation, Condition — and the interaction patterns, which is why FHIR clients are portable across servers.

How do I know which resources and searches this server supports?

Request `/baseR4/metadata`, which returns a CapabilityStatement — a machine-readable declaration of every resource type, interaction and search parameter the server implements. Every conformant FHIR server publishes one.

Tools that pair with this API

JSON Formatter

Format, beautify and minify JSON online with 2-space, 4-space or tab indentation. Sort keys alphabetically and catch syntax errors instantly — free and private.

JSON Viewer

View JSON as a collapsible interactive tree online. Expand and collapse nodes, search keys and values, and copy the JSONPath of any node privately.

JSON Schema Validator

Validate JSON against a JSON Schema online. Checks type, required, properties, enum, pattern and more, listing every failure with its JSON Pointer.

HAPI FHIR Test Server is an independent third-party service and is not affiliated with ByteTools or ByteVancer. Details on this page were verified on 2026-08-21; always check the official documentation before relying on this API in production, as terms and limits can change.