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.

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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

{
  "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:

<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.