Crossref Has a Free API — Search 150M+ Scholarly Articles (No Key Required)

I was building a research tool and needed article metadata — titles, authors, citations, DOIs. I tried Google Scholar (no API), Semantic Scholar (rate limited), Web of Science (expensive). Then I found Crossref — and it changed everything. What is Crossref? Crossref is the official DOI registration agency. When a publisher assigns a DOI to an article, the metadata goes to Crossref. That means: 150M+ scholarly works — journal articles, books, conference papers, datasets No API key — just send a request No rate limits — with polite pool (add your email) Rich metadata — citations, references, funders, licenses Quick Example import requests response = requests . get ( " https://api.crossref.org/works " , params = { " query " : " machine learning healthcare " , " rows " : 5 , " mailto " : " your@email.com " # polite pool = faster } ) for item in response . json ()[ " message " ][ " items " ]: title = item [ " title " ][ 0 ] citations = item . get ( " is-referenced-by-count " , 0 ) doi = ite