ChEBI (Chemical Entities of Biological Interest) API Reference

Base URLs

OLS (Ontology Lookup Service) API: https://www.ebi.ac.uk/ols4/api
ChEBI Web Services (SOAP): https://www.ebi.ac.uk/webservices/chebi/2.0/test (SOAP/XML only)
ChEBI LibChebi REST (limited): entity pages at https://www.ebi.ac.uk/chebi

Authentication

None required. All endpoints are public.

Rate Limits

No published hard limits. EBI general guidance: reasonable usage.

Important Note

ChEBI's primary web service is SOAP-based (XML), not REST. For REST-style JSON access, use the EBI OLS4 API which indexes ChEBI as an ontology.

OLS4 API Endpoints (Recommended for REST/JSON)

1. Search ChEBI Terms

GET https://www.ebi.ac.uk/ols4/api/search?q={query}&ontology=chebi

Example:

GET https://www.ebi.ac.uk/ols4/api/search?q=aspirin&ontology=chebi

Returns JSON with matching ChEBI terms, IDs, definitions, synonyms.

2. Lookup by ChEBI ID

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi/terms?iri=http://purl.obolibrary.org/obo/CHEBI_{id}

Example:

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi/terms?iri=http://purl.obolibrary.org/obo/CHEBI_15365

Returns full term details: name, definition, synonyms, xrefs, relationships.

3. Get Term by Short Form

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi/terms/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCHEBI_{id}

(Double-encoded IRI in path.)

4. Term Hierarchy — Parents

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi/terms/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCHEBI_{id}/parents

5. Term Hierarchy — Children

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi/terms/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCHEBI_{id}/children

6. Ontology Metadata

GET https://www.ebi.ac.uk/ols4/api/ontologies/chebi

OLS Search Response Format

json

{
  "response": {
    "numFound": 5,
    "docs": [
      {
        "id": "chebi:15365",
        "iri": "http://purl.obolibrary.org/obo/CHEBI_15365",
        "label": "aspirin",
        "description": ["A member of the class of benzoic acids..."],
        "short_form": "CHEBI_15365",
        "obo_id": "CHEBI:15365",
        "ontology_name": "chebi",
        "type": "class"
      }
    ]
  }
}

ChEBI SOAP Web Service (Alternative)

If you need chemical-specific data (formula, mass, structure, InChI), use the SOAP service:

WSDL: https://www.ebi.ac.uk/webservices/chebi/2.0/webservice?wsdl
Operations: getCompleteEntity, getLiteEntity, getStructureSearch, getOntologyChildren, getOntologyParents
Returns XML only.

Example SOAP request for getCompleteEntity:

xml

<soapenv:Body>
  <chebi:getCompleteEntity>
    <chebi:chebiId>CHEBI:15365</chebi:chebiId>
  </chebi:getCompleteEntity>
</soapenv:Body>

Returns: formula, mass, charge, InChI, InChIKey, SMILES, synonyms, database links, ontology parents/children.

Notes

For programmatic REST access, OLS4 is the easiest path.
For chemical structure searches (by InChI, SMILES, substructure), the SOAP service is required.
ChEBI IDs are numeric (e.g., 15365) but referenced as "CHEBI:15365" in OBO format.
PubChem and UniChem can cross-reference ChEBI IDs to other chemical databases.