FHIR Resource Inspector
Click any element of a FHIR resource to see its type, cardinality, definition, valid choice types and FHIRPath, for R4, R4B and R5.
How to use the Resource Inspector
- Choose the FHIR version: R4, R4B or R5.
- Paste a resource to list the elements it contains, then select one. Or type any element path, such as
Observation.value[x]orEncounter.class, without pasting anything. - See what the specification says about it: data type(s), cardinality, short description and full definition, the binding strength for coded elements, allowed reference targets, and for choice elements the list of allowed types.
- Copy the element's FHIRPath, or open the resource in another tool.
The definitions come from the official HL7 specification files for each version and are loaded on demand.
Questions it answers quickly
| Question | Look up |
|---|---|
Is name an array? | Patient.name: cardinality 0..*, so yes |
| What types can an Observation value be? | Observation.value[x]: Quantity, CodeableConcept, string, boolean, integer, Range, Ratio, SampledData, time, dateTime, Period (plus Attachment and Reference in R5) |
What can subject point at? | Observation.subject in R4: Patient, Group, Device, Location |
Must status use a fixed list of codes? | Observation.status: binding required, so only the specification's codes are valid |
| Did this element change in R5? | Switch the version and compare. Encounter.class is a single Coding in R4 and a CodeableConcept array in R5 |
Reading cardinality
0..1— optional, at most one: a single value, never an array.1..1— required, exactly one.0..*— optional, repeating: always an array in JSON, even with one item.1..*— required, at least one.
Profiles such as US Core can tighten these (make an optional element required, or limit a repeating element to one), but they can't loosen them. The inspector shows the base specification.
Limitations
- It shows base resource definitions only, not profiles or implementation guides.
- It describes elements, but it doesn't validate your resource. Use the Validator for that.
FAQ
Where else can I browse definitions?
The R4 and R5 reference pages show the full element table, example JSON and search parameters for the most-used resources and data types. The R4 vs R5 comparison lists what changed.
Is my resource uploaded?
No. The resource you paste is only used to list its elements in this page. The definitions are static files from this site, generated from the HL7 specification.
Why does an element show a different type in R4 and R5?
Some elements changed between versions. Encounter.class, for example, is a Coding in R4 and an array of CodeableConcept in R5. Switching the version selector shows each definition.
Does it show profile constraints, such as US Core?
No. It shows the base specification. Profiles can make elements required or limit cardinality, so check the implementation guide for those.
FHIR Toolbox is a free collection of HL7 FHIR tools by Omindra Labs. The tools process your data in your browser; it is not uploaded for normal tool operations.