The tools listed below can help you determine whether a journal or publisher is predatory.
BeInformed Checklist - Developed by the Duke University Medical Library and Archives, this checklist for authors to evaluate journals/publishers.
If you are considering publishing in an open access journal, membership in Directory of Open Access Journals or the Open Access Scholarly Publishers Association is a good indication a journal is not predatory.
How Do I Know If I'm Submitting to a Predatory Journal - This guide, geared toward those in the biological and chemical sciences, was developed by MD Anderson Cancer Center.
Hijacked Journal Checker - According to the website: “Hijacked journals mimic legitimate journals by adopting their titles, ISSNs, and other metadata. Usually, hijacked journals mirror legitimate journals without permission from the original journal; at rare times, however, publishers will buy rights to a legitimate journal but continue the publication under considerably less stringent publishing protocols and without clearly noting to the reader the change in ownership or publication standards (sometimes known as “cloned” journals).” This list is compiled by Retraction Watch.
Journal Evaluation Tool - Created by librarians at Loyola Marymount University, this document provides a rubric for evaluating potentially predatory journals.
Ten Simple Rules for Avoiding Predatory Publishing Scams - This article from the PLOS's Computational Biology provides guidance on avoiding predatory publishers.