Open metadata APIs: Consensus, OpenAlex, Semantic Scholar and Crossref

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What each API does best

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Semantic search compared

• OpenAlex semantic search (search.semantic) embeds each work’s title, abstract and venue name. It returns up to 50 results per query, at 1 request a second, and supports 17 filters. Filters such as cited_by_count aren’t supported⁷. Its regular search matches title, abstract, full text and keywords⁸.
• Semantic Scholar offers relevance search (up to 1,000 ranked results), Boolean bulk search, and snippet search, which returns passages of about 500 words from the paper body⁹.
• Crossref searches bibliographic metadata⁴.
• Consensus runs semantic and keyword search together over 400M+ articles and ranks for scientific relevance. Every filter combines with the search, and a query returns up to 1,000 results.

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Evidence metadata

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Enrich Consensus results with open metadata

import os
import requests

papers = requests.get(
    "https://api.consensus.app/v1/search",
    headers={"x-api-key": os.environ["CONSENSUS_API_KEY"]},
    params={"query": "does creatine improve working memory", "study_types": "rct,meta-analysis"},
    timeout=30,
).json()["results"]

for paper in papers:
    if not paper["doi"]:
        continue
    # Authors, institutions and funders from OpenAlex
    work = requests.get(f"https://api.openalex.org/works/doi:{paper['doi']}", timeout=30).json()
    # Citations from Semantic Scholar
    s2 = requests.get(
        f"https://api.semanticscholar.org/graph/v1/paper/DOI:{paper['doi']}",
        params={"fields": "citationCount,citations.title"},
        timeout=30,
    ).json()
    print(paper["title"], paper["study_type"], work.get("cited_by_count"), s2.get("citationCount"))

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Licences and terms

• OpenAlex: all data is CC0¹.
• Semantic Scholar: data is licensed CC BY-NC or ODC-BY, and you must attribute Semantic Scholar. AI2 uses the data you send to the API to provide and improve it¹².
• Crossref: most metadata isn’t subject to copyright and can be used for any purpose. Some abstracts are copyrighted by publishers or authors⁴.
• Consensus: customer data isn’t used to train AI models. See Pricing, rate limits and data privacy.

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The same question on each API

curl -G "https://api.consensus.app/v1/search" -H "x-api-key: $CONSENSUS_API_KEY" \
  --data-urlencode "query=does creatine improve working memory" \
  --data-urlencode "study_types=rct,meta-analysis"

curl -G "https://api.openalex.org/works" \
  --data-urlencode "search=creatine working memory" \
  --data-urlencode "filter=study_designs.id:randomized-controlled-trial" \
  --data-urlencode "api_key=$OPENALEX_API_KEY"

curl -G "https://api.semanticscholar.org/graph/v1/paper/search" \
  --data-urlencode "query=creatine working memory" \
  --data-urlencode "publicationTypes=ClinicalTrial" \
  --data-urlencode "fields=title,year,publicationTypes,citationCount" \
  -H "x-api-key: $S2_API_KEY"

curl -G "https://api.crossref.org/works" \
  --data-urlencode "query=creatine working memory" \
  --data-urlencode "[email protected]"

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Related

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Sources

1. OpenAlex pricing: all data CC0; $1 of free API usage a day with a key; annual plans from $5,000 a year; the whole database can be downloaded as a snapshot refreshed every quarter. A keyless response notes that it shares a $0.10 daily budget per IP address.
2. OpenAlex works: more than 320 million works in the core catalog.
3. Semantic Scholar API overview: 214 million papers; unauthenticated requests share 1,000 requests a second across all users and may be throttled under heavy use; the introductory limit for an API key is 1 request a second. The API also serves SPECTER2 embeddings and a Recommendations service for similar papers.
4. Crossref REST API: bibliographic metadata including funding, licence and abstracts; no sign-up required; most metadata isn’t subject to copyright.
5. Tips for using the Crossref REST API: annual public data file.
6. total-results from https://api.crossref.org/works?rows=0 on 5 November 2026: 188,499,975.
7. OpenAlex semantic search: embeds title, abstract and venue name; up to 50 results per query; 1 request a second; 17 supported filters, and others such as cited_by_count return a 400 error.
8. OpenAlex search: search= matches works by title, abstract, full text and keywords; Boolean and phrase searches are supported.
9. Semantic Scholar Academic Graph API reference: /paper/search (up to 1,000 relevance-ranked results), /paper/search/bulk (Boolean), /snippet/search (passages of about 500 words from title, abstract and body), and the publicationTypes, minCitationCount and venue filters.
10. OpenAlex study designs: seven designs tagged automatically from title and abstract; each value right at least 96% of the time.
11. OpenAlex single entities: lookups by ID or DOI, such as /works/doi:10.7717/peerj.4375, are free.
12. Semantic Scholar API License Agreement: AI2 uses the data you send to call the API “for the purpose of providing and improving the API”; data is licensed CC BY-NC or ODC-BY; attribution required.