Indexes
An index is an external bibliographic index or registry that a work can be listed in — Crossref, PubMed, DataCite, DOAJ, arXiv. Indexes are a vocabulary: they’re not native, judgment-call IDs, just consistent handles on crisply-existing external lists. A single work can appear in several indexes at once, so each work carries an indexed_in list, and a source records which of these indexes cover it. An index’s OpenAlex ID looks like https://openalex.org/indexes/doaj; fetch one at api.openalex.org/indexes/doaj.
How we build it
The list is the set of external indexes and registries OpenAlex tracks as sources of works: DOI-registration agencies (Crossref, DataCite), curated indexes (DOAJ, PubMed), and a preprint repository (arXiv). We record which of them lists each work; a work can be in more than one. There are 5 indexes.
Values
The complete list of all 5 indexes:
| ID | Display name | What it indexes |
|---|---|---|
crossref |
Crossref | The largest DOI-registration agency: journal articles, books, conference proceedings |
pubmed |
PubMed | The National Library of Medicine’s biomedical and life-sciences literature |
datacite |
DataCite | A DOI-registration agency focused on research data and other non-traditional outputs |
doaj |
DOAJ | The Directory of Open Access Journals, a curated index of peer-reviewed OA journals |
arxiv |
arXiv | The open-access preprint repository for physics, math, CS, and related fields |
The live list is at api.openalex.org/indexes.
Fields
The top-level fields on an index object. Fields shared with other entities (id, display_name, works_count, cited_by_count, created_date, updated_date) are documented once on Common fields.
id
String. The OpenAlex ID for this index, e.g. https://openalex.org/indexes/doaj. See Common fields.
display_name
String. The index’s name, e.g. DOAJ. See Common fields.
description
String. A short one-line description of the index and what it covers.
works_count
Integer. How many works are listed in this index. See Common fields.
cited_by_count
Integer. Total citations across those works. See Common fields.
works_api_url
String. A ready-made Works API URL for every work in this index (filter=indexed_in:<ID>).
created_date
String. When the index record was added to OpenAlex (YYYY-MM-DD). See Common fields.
updated_date
String. When the index record last changed. See Common fields.
In the API
The Indexes endpoint is at api.openalex.org/indexes. Fetch one by ID — /indexes/doaj — or list all five.
Indexes are most useful as a filter on works: filter=indexed_in:doaj returns works listed in DOAJ, filter=indexed_in:crossref those with a Crossref record, and group_by=indexed_in breaks a result set down by index. On sources, the same information appears as which indexes cover the source. See Filtering for the full syntax and the endpoints index for every endpoint.