Ocean of Papers — free research paper search, open-access PDFs and citation maps

Search 250M+ research papers and get Free PDF downloads of open-access papers. No sign-up. One search across PubMed, arXiv, OpenAlex and Europe PMC, plus DOI lookup and citation maps.

Everything you need to find, map and organise research

Search six academic databases at once, see how papers connect on a citation map, and keep what matters in projects you can export anywhere.

  1. Search: Type a topic, title, author or DOI. Results come from OpenAlex, PubMed, arXiv, bioRxiv, medRxiv and Europe PMC.
  2. Map: Open a citation map from any paper to see related work, what it builds on and what came after.
  3. Save & export: Save papers to projects with notes and tags, then export BibTeX, RIS or CSV for your reference manager.

See how a field connects, starting from one paper

Start from any paper and get a map of about 30 related papers (choose 15, 30 or 50). Bigger circles are more cited, darker circles are newer, and lines are real citation links.

  • Lines show direct citations, shared references, co-citation or a shared author. Click a line to see why two papers are linked.
  • Switch between Similar, Prior works and Derivative works.
  • Explore similar, earlier or later work, or the same authors, and add papers to the map.
  • Use “Add as seed” to map several papers together, and step back and forward through your history.
  • Export as PNG, BibTeX, RIS or CSV, or share a link to the map.
  • Free plan: 5 new maps a month. Switching modes and expanding a map don’t count.

Watch a topic develop over time

The same papers laid out by year and citation count (log scale), so you can see the early foundations and how the field grew from them.

  • Years across, citations up
  • Same papers, links and colours as the graph
  • One click to switch between Graph and Timeline

Find the papers your project is missing

Discover ranks papers by how closely they connect to the ones already in your project, and tells you why each one is there.

  • Reasons like “Cited by 4 of your papers”, “Cites 3 of your papers”, “Similar to 2 papers” or “By A. Smith, in your project”
  • Add a suggestion in one click
  • Suggestions refresh as your project grows

Keep your reading organised

Group papers into projects with notes and tags. Bring in what you already have and export it again whenever you need to.

  • Import from Zotero, a BibTeX or RIS file, or a list of DOIs
  • Export BibTeX, RIS or CSV for Zotero, Mendeley or EndNote
  • Saving papers needs a free account

Sort through many results quickly

Scan results as a compact table, or go through them one card at a time in Swipe view, saving what’s relevant and skipping the rest.

  • Table view for side-by-side scanning
  • Swipe view to save or skip papers one at a time

At a glance

What it is
A free academic search engine with open-access PDFs and citation maps.
Data sources
OpenAlex, PubMed, arXiv, bioRxiv, medRxiv, Europe PMC (6 sources, 250M+ papers).
PDFs
Legal open-access PDFs via Unpaywall, PubMed Central, arXiv, bioRxiv and medRxiv.
Citation maps
Map one paper or several together in three modes: Similar, Prior works and Derivative works (cited by), as a graph or a timeline. Links come from citation data (direct citations, shared references, co-citation, shared authors).
Export
BibTeX, RIS, CSV and text; per-paper APA, MLA, Chicago, Harvard, Vancouver and BibTeX citations.
Account
Not needed to search, open PDFs, export or build maps. A free account saves papers to a library that syncs across devices.
Free plan
Unlimited search, PDFs and exports, plus 5 new citation maps per month.
Pro
Unlimited citation maps and priority support for $9/month or $79/year (₹299/month or ₹2,499/year in India).
Import
Bring papers in from Zotero (one-time import), BibTeX or RIS files, or a list of DOIs.
Project suggestions
Discover ranks papers a project is missing (cited by, citing or similar to its papers, or by the same authors).
Not yet available
Email alerts for new papers, two-way Zotero sync and shared projects.

Frequently asked questions

How do I search for research papers for free?

Type a topic, title, author or DOI into the search bar. Ocean of Papers searches over 250 million papers across OpenAlex, PubMed, arXiv, bioRxiv, medRxiv and Europe PMC for free, with no login required.

How do I download research papers as PDFs?

Ocean of Papers uses Unpaywall, PubMed Central, arXiv, bioRxiv and medRxiv to find free, legal open-access PDFs. Click the PDF button on any result to open or download the paper.

What databases does Ocean of Papers search?

Six sources: OpenAlex (250M+ works), PubMed (biomedical), arXiv (physics, maths and CS preprints), bioRxiv and medRxiv (biology and medicine preprints) and Europe PMC.

Can I export search results or citations?

Yes. Export results as BibTeX, RIS, CSV or a text file, copy DOIs to the clipboard, or use the Cite button for APA, MLA, Chicago, Harvard, Vancouver or BibTeX. RIS and BibTeX files import into Zotero, Mendeley and EndNote.

Is Ocean of Papers a free alternative to Connected Papers or ResearchRabbit?

Yes. You can build a citation map from any search result in Similar, Prior or Cited-by mode. The free plan includes 5 new maps per month; Pro unlocks unlimited maps for $9/month.

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