OAIster is a freely accessible search engine for open access web resources, available from OCLC. OAIster uses the Open Access Initiative Protocol for Metadata Harvesting (OAI-PMH) to harvest records from websites. OAIster contains over 25 million records from all disciplines and subjects contributed by over 1,000 libraries, archives, and repositories. The records harvested by OAIster use Dublin Core (unqualified) metadata format. Repository managers running OAI-compliant repositories can contribute records for open access web resources. OAIster records can be searched separately at the website, and are incorporated into OCLC Worldcat.