BASE is one of the world's most voluminous search engines especially for academic open access web resources. BASE is operated by Bielefeld University Library.

As the open access movement grows and prospers, more and more repository servers come into being which use the "Open Archives Initiative Protocol for Metadata Harvesting" (OAI-PMH) for providing their contents. BASE collects, normalises, and indexes these data. BASE provides more than 80 million documents from more than 4,000 sources. You can access the full texts of about 60-70% of the indexed documents. The index is continuously enhanced by integrating further OAI sources as well as local sources. Our OAI-PMH Blog communicates information related to harvesting and aggregating activities performed for BASE.

BASE is a registered OAI service provider and contributed to the European project "Digital Repository Infrastructure Vision for European Research" (DRIVER). Database managers can integrate the BASE index into your own local infrastructure (e.g. meta search engines, library catalogues) via an interface.

In comparison to commercial search engines, BASE is charcterised by the following features of the Intellectually selected resources:

1.Only document servers that comply with the specific requirements of academic quality and relevance are included
2. A data resources inventory provides transparency in the searches
3. Discloses web resources of the "Deep Web", which are ignored by commercial search engines or get lost in the vast quantity of hits.
4. The display of search results includes precise bibliographic data
5. Several options for sorting the result list
6. "Refine your search result" options (by author, subject, DDC, year of publication, collection, language and document type)
7. Browsing by DDC (Dewey Decimal Classification) and document type.