Predatory publishing generally refers to the systematic for-profit publication of purportedly scholarly content (in journals and articles, monographs, books, or conference proceedings) in a deceptive or fraudulent way and without any regard for quality assurance. (Definition taken from COPE - Committee on Publication Ethics)

Further information

• Beall's List is a resource that helps you find out whether an OA journal that you plan to publish with is considered questionable or predatory: https://beallslist.net/
  

• More detailed information about the practice of predatory publishing and why it harms the reputation of scientists and Open Access Journals can be found in this discussion paper compiled by COPE: https://publicationethics.org/files/cope_dd_a4_pred_publishing_nov19_screenaw.pdf
  

HALis an open archive where authors can deposit scholarly documents from all academic fields. It has a good position in the international web repository ranking

https://uk.sagepub.com/en-gb/eur/science-communication/journal200892