There is no perfect way to know! It takes research. Quality is on a spectrum and there are a variety of tools/measures.
 

How do I measure journal quality?

There are many tools for this! You do not need to use all the tools in this list!

• SCOPUS Index List: view the journal's CiteScore and other metrics. 
• Harzing Journal Quality list: for academic journals in the following broad areas: Economics, Finance, Accounting, Management, and Marketing. Scroll to the "Download Information" section to see the list by title, subject area, and ISSN.
• Directory of Open Access Journals (DOAJ): The DOAJ carefully vets open-access journals for inclusion, so if the journal is not listed in the DOAJ, it may be questionable.
• Committee on Publication and Ethics (COPE): If a journal is not listed here, it is not a member and is likely not following their best practices. 
• Scimago Journal & Country Rank (SJR): shows if a journal is indexed in a major citation database. It can also help you identify journals in your subject area.
• Journal Citation Reports database (not available through Lynn Library): Uses Impact Factor to rank journals. Only journals vetted through the JCR can officially state that they have an Impact Factor (Caution, predatory journals will list a fake Impact Factor). 
  • Journal Citation Indicator scores are visible for some ProQuest journals when using Lynn's "Journals A-Z" to look up the journal (link on the library home page).
• Journal Guide: A tool to help researchers evaluate scholarly journals and choose the right journal for their publications. They use the impact metric Source-Normalized Impact per Paper (SNIP); a new metric based on Scopus. SNIP is temporarily used in place of Journal Impact Factors, pending permission to use JIFs again (they were able to include the Impact Factor in the past and hope to again). 
• EigenFactor Search: Measures a journal's total importance to the scientific community with more weight given to citations from significant and larger journals. The score measures the average influence of each article over the first five years after publication.
• Scimago Journal Rank (SJR): A measure of the scientific influence of scholarly journals that accounts for the number of citations received by a journal and the importance or prestige of the journals.
• PlumMetrics: is the word coined for EBSCO's altmetrics scholar citation score that includes uses, captures, mentions, and social media metrics (available through Lynn University Library).

• A journal that uses the open-access model to gain credibility, but the journal is not reputable or is a scam.
• Their main goal is profit, and they provide no editorial services or peer-review but require authors to pay to be published.  
• They often require authors to sign away copyright, aggressively target authors, and lack transparency about the publishing process.
• Generally the articles published in these journals receive no citations over the first five years of publication (see the list above for citation metrics tools).

How do I identify a predatory journal?

There are ways that predatory journals stand out.

• Visit the journal website. Use the checklist from the Think. Check. Submit. website to evaluate a journal. Are they transparent about the peer-review process? Are there fees? Do they include contact information for the publisher and editors? Are there spelling or grammatical mistakes?
• Google the journal title and the word predatory. You may be able to easily find news stories about the journal and its predatory practices. 
• Check the Beall's List of Potential Predatory Journals and Publishers. It is an archived list (last updated December 8, 2021).
• Be cautious about "Impact Factors." Many predatory journals will make up an impact factor to appear reputable.

This article may help.