Crossref API: Search 140M+ Academic Papers by DOI, Author, or Journal (Free, No Key)

The Hidden Giant of Academic APIs Everyone talks about Google Scholar, but Crossref quietly indexes 140 million+ scholarly works with a completely free API. No API key. No signup. No rate limit headaches. If you need DOI metadata, citation counts, journal information, or funder data — Crossref is the canonical source. Most academic publishers register their DOIs here. Quick Start: Search by Keyword import requests def search_papers ( query , rows = 5 ): url = " https://api.crossref.org/works " params = { " query " : query , " rows " : rows , " sort " : " relevance " , " select " : " DOI,title,author,published-print,is-referenced-by-count " } # Polite pool: add your email for faster responses headers = { " User-Agent " : " MyApp/1.0 (mailto:your@email.com) " } resp = requests . get ( url , params = params , headers = headers ) for item in resp . json ()[ " message " ][ " items " ]: title = item [ " title " ][ 0 ] if item . get ( " title " ) else " No title " citations = item . get ( " i