Predatory publishers are entities which produce open access journals that:

• Prioritize self-interest at the expense of scholarship
• Use false or misleading information
• Deviate from best editorial and publication practices including rigorous peer review
• Lack transparency
• Use aggressive and indiscriminate solicitation practices
• Exhibit a spectrum of behaviors that range from genuinely fraudulent with varying degrees of unacceptable practices including well-intentioned but low-quality standards

Sources:
Grudniewicz A, Moher D, Cobey KD, et al. Predatory journals: no definition, no defence. Nature. 2019;576(7786):210-212.
The InterAcademy Partnership (IAP). Combatting predatory academic journals and conferences. 2022.

• Content may be inaccurate and could adversely affect patient care decisions
• Citing erodes the scientific body of literature
• Your research is less likely to be cited and may not be permanently archived
• The Mayo Clinic Academic Appointments and Promotions Committee recognizes neither publications nor editorial positions associated with questionable journals
• It may be difficult and costly to withdraw 
• There may be potential consequences for future grant funding

Scrutinize journal websites with more than one of these traits:

• Very broad scope
• False metrics and claims of indexing by scholarly databases (e.g. Embase, Medline, Scopus, Web of Science)
• Odd grammar & spelling errors 
• Unprofessional images of editorial board members
• Dysfunctional links 
• Homepage language targets authors rather than readers
• Promise of quick publication turn-around time within a few weeks
• Lack of information about research misconduct, licensing and copyright
• Contact information is sketchy