Cabells is a database which lists predatory journals, not recommended as publication channels. The service is in test use in University of Helsinki until the end of 2023. UH has a license to a list of predatory journals (predatory reports). From the search result you can see a list of suspicious features of the journal (violations) which are the reasons why the journal is added to the database. Note that Cabells has no relation to a website Predatoryreports.org. There is no guarantee that the information there is reliable.
BASE (Bielefeld Academic Search Engine)
BASE provides more than 300 million documents from more than 10,000 content providers. You can access the full texts of about 60% of the indexed documents for free (Open Access).
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CORE (COnnecting REpositories)
CORE’s mission is to aggregate all open access research outputs from repositories and journals worldwide and make them available to the public.