Journal Citation Reports (JCR) is sourced from Web of Science Core Collection, the premier citation index on the Web of Science platform. Journals must undergo a rigorous evaluation by our editorial team in order to be covered in Web of Science Core Collection. We capture the cited references for all content from these journals, and we link those cited references to the cited papers. This article-level citation data is aggregated to the journal-level at the end of the year to create the indicators available in JCR. Over 11,500 titles from the Science Citation Index-Expanded and Social Sciences Citation Index are covered in JCR. The Science and Social Science editions of JCR are released annually.

Journal Impact Factor (JIF)
The Journal Impact Factor identifies the frequency with which an average article from a journal is cited in a particular year. You can use this number to evaluate or compare a journal’s relative importance to others in the same field or see how frequently articles are cited to determine which journals may be better for your collection.

JIF Quartile
A journal's quartile ranking is determined by comparing a journal to others in its JCR category based on Impact Factor score. If a journal falls in Q1, it means that the journal performs better than at least 75% of journals in that category, based on its Impact Factor score.

JIF Percentile
The journal’s rank in category, determined by Impact Factor, expressed as a percentile. For example, a journal with a JIF percentile of 89 performs better than 89% of journals in that category, based on its Impact Factor score. JIF percentiles give you a more granular view than quartiles do.

Source: https://clarivate.libguides.com/jcr/

Source: https://clarivate.libguides.com/ld.php?content_id=55911188