Cito does not crawl the web or generate any records itself. The corpus is built from two open scholarly datasets, mirrored locally and kept in sync with their upstream releases.

Sources

• Semantic Scholar (Allen Institute for AI) provides the backbone: paper metadata, abstracts, citation counts and the SPECTER2 embeddings behind semantic search. Result IDs are Semantic Scholar CorpusIDs.
• OpenAlex fills in what open access adds after publication: direct PDF links for papers with a free, legal copy, plus abstracts for papers where Semantic Scholar has none. Records are joined by DOI.

Coverage

Honest limits: abstract coverage is partial (some publishers do not license abstracts for redistribution), citation counts lag the very newest papers, DOIs are missing on much older and informally published work, and Cito has no full text. The pdf_url field links to the copy at its origin; nothing is proxied or re-hosted.

Publication years

Fields of study

Semantic Scholar's coarse subject labels. Multi-label: a paper spanning two disciplines counts under both, so shares add up to more than 100%.

Publication types

Document types from Semantic Scholar. Multi-label, so a paper can carry more than one tag.

Freshness and update schedule

The current corpus snapshot is 2026-06-24. Every API response echoes this as corpus_release, so you always know exactly which version of the corpus produced a result.

• Roughly every two weeks: new, updated and withdrawn papers from the latest Semantic Scholar releases are merged into all indexes. Freshly added papers are enriched with OpenAlex open-access data in the same pass.
• Quarterly: recent papers that still lack a PDF link get re-checked against OpenAlex. Open-access records improve after the fact (a repository copy often appears months after publication), so a paper that had no free PDF at ingest may gain one later.

Expect a paper to be findable in Cito within about two weeks of it entering Semantic Scholar. If you need same-day coverage of brand-new preprints, query the preprint server directly; Cito optimizes for breadth, ranking quality and throughput rather than same-day recall.

Reproducibility

Search ordering is deterministic within a snapshot, and the published_before parameter gives a leak-safe date cutoff (papers whose date cannot prove precedence are excluded, not guessed). Together with corpus_release, this makes runs replayable: useful for benchmarks, agent evaluations and citation audits.