FHIR Extension Data Type (R4)

Extension adds data that the base specification doesn't define. Element table, example JSON and FHIRPath for FHIR R4.

FHIR Extension Data Type (R4) — part of the free FHIR Toolbox library.
Runs entirely in your browser: your FHIR data is never uploaded to a server.

Overview

Extension adds data that the base specification doesn't define. Each has a url that identifies its definition and exactly one value[x] (or nested extensions). Modifier extensions use modifierExtension and change the meaning of the resource.

Elements

Element	Type	Cardinality	Description
Extension.url	String	1..1	identifies the meaning of the extension
Extension.value[x]	base64Binary \| boolean \| canonical \| code \| date \| dateTime \| decimal \| id \| instant \| integer \| markdown \| oid \| positiveInt \| string \| time \| unsignedInt \| uri \| url \| uuid \| Address \| Age \| Annotation \| Attachment \| CodeableConcept \| Coding \| ContactPoint \| Count \| Distance \| Duration \| HumanName \| Identifier \| Money \| Period \| Quantity \| Range \| Ratio \| Reference \| SampledData \| Signature \| Timing \| ContactDetail \| Contributor \| DataRequirement \| Expression \| ParameterDefinition \| RelatedArtifact \| TriggerDefinition \| UsageContext \| Dosage \| Meta	0..1	Value of extension

Example JSON (R4)

{
  "url": "http://hl7.org/fhir/StructureDefinition/patient-birthPlace",
  "valueAddress": {
    "city": "Boston",
    "state": "MA",
    "country": "US"
  }
}

FHIRPath

Patient.extension('http://hl7.org/fhir/StructureDefinition/patient-birthPlace').value — Read an extension's value

FHIR Toolbox is a free, privacy-first collection of HL7 FHIR utilities by Omindra Labs. Every tool performs zero-server processing — your health data never leaves your device.