Journal Impact Factor* is a metric that measure ratios of citations that papers in a given journal have received in one year, to those received in previous years.
A journal's Impact Factor is often publicised on its homepage, and there are tools available to benchmark metrics against one another. Journal Impact Factor is not freely available - apart from when advertised on individual homepages - but available via subscription to Journal Citation Reports.
It's important to recognize that Journal Impact Factor was originally created to help librarians decide what journals to purchase, not as a metric for individual article quality (DORA, n.d.). Further, like any other metric, Journal Impact Factor has several faults chief of which are that the number of citations received by articles in a journal (citation distribution) can be highly skewed (Seglen, 1997). For further information and best practices when using Journal Impact Factor, please consult DORA.
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Starting from the 2025 release (using 2024 data), JIF calculations will exclude citations to and from retracted content in the numerator meaning that these citations will not contribute to the numerical value of JIF (Journal Citation Reports 2025, 2025). However, Clarivate will still be including retracted articles in the total article count (JIF denominator) in order to maintain "transparency and accountability" (Journal Citation Reports 2025, 2025).
