BASE
Bielefeld Academic Search Engine — one of the largest indexes of the academic open web.
At a Glance
- Publisher
- Bielefeld University Library
- Coverage
400M+ documents harvested from 11,000+ repositories, including much grey literature and non-English content (verify current counts).
- Access
Free; OAI-PMH harvesting; API available.
- Free alternative
- It is free; CORE, OpenAlex.
- Regional
Global; strong repository and non-English coverage.
Our Take
BASE is a huge, repository-driven index of the scholarly open web — run by a university library, it harvests hundreds of millions of documents including the grey literature and non-English material the commercial indexes skip. Its filters, by document type, access, and subject class, are genuinely useful for scoping. Like other harvest-based tools, it prioritises breadth over curation, so expect variable metadata. Use it to find repository-hosted and grey literature, especially outside English; verify specifics elsewhere.
Power Tips
- Filter by document type and open-access status to scope a grey-literature search.
- Use BASE to surface non-English and repository content the big indexes miss.
- Combine with CORE and OpenAlex for fuller open-access coverage.
Alternatives & Complements
CORE, OpenAlex, Unpaywall, DOAJ
Figures last verified: June 15, 2026