This article provides a comparative analysis of the journal coverage of three scholarly databases—Web of Science, Scopus, and Dimensions. The study aims to describe, understand, and visualize the differences in journal coverage among these databases. Using the most recent master journal lists, the analysis reveals that Web of Science is the most selective, followed by Dimensions, which is the most exhaustive. About 99.11% and 96.61% of the journals indexed in Web of Science are also indexed in Scopus and Dimensions, respectively. Scopus has 96.42% of its indexed journals covered by Dimensions. Dimensions has 82.22% more journals than Web of Science and 48.17% more journals than Scopus. The study also analyzed research outputs for 20 selected countries from 2010 to 2018, finding significant variations in research output volume, rank, global share, and subject area composition across the databases. The results highlight the need for a comprehensive understanding of the differences in journal coverage to ensure fair and accurate research evaluation.This article provides a comparative analysis of the journal coverage of three scholarly databases—Web of Science, Scopus, and Dimensions. The study aims to describe, understand, and visualize the differences in journal coverage among these databases. Using the most recent master journal lists, the analysis reveals that Web of Science is the most selective, followed by Dimensions, which is the most exhaustive. About 99.11% and 96.61% of the journals indexed in Web of Science are also indexed in Scopus and Dimensions, respectively. Scopus has 96.42% of its indexed journals covered by Dimensions. Dimensions has 82.22% more journals than Web of Science and 48.17% more journals than Scopus. The study also analyzed research outputs for 20 selected countries from 2010 to 2018, finding significant variations in research output volume, rank, global share, and subject area composition across the databases. The results highlight the need for a comprehensive understanding of the differences in journal coverage to ensure fair and accurate research evaluation.