<p>This study examines temporal disciplinary and regional journal coverage in Web of Science and Scopus between 2004 and 2024. Journal data were extracted from Clarivate’s InCites (Web of Science) and Scimago Journal Rank (Scopus) and compared with Ulrich’s Periodicals Directory as a baseline. Journals from the three sources were mapped to disciplines and world regions to analyse relative coverage. The yearly trend in relative coverage by Web of Science and Scopus—whether increasing or declining over time—was statistically evaluated using the Mann–Kendall test implemented in R. Natural Sciences, Engineering and Technology, and Medical and Health Sciences remained consistently overrepresented in both databases despite stable or declining global shares. Conversely, Agricultural and Veterinary Sciences, Social Sciences, and Arts and Humanities stayed underrepresented, although their coverage shares were stable or slightly increasing. Regionally, Sub-Saharan Africa and Central and Southeast Asia increased their share of journals in Ulrich but became more underrepresented in Web of Science and Scopus. Eastern and Southeast Asia and Latin America and the Caribbean reduced their Ulrich shares but expanded their presence in both databases, narrowing underrepresentation. North America’s Ulrich share declined marginally, but its previously strong overrepresentation in Web of Science and Scopus fell sharply. Europe’s Ulrich share decreased while its share—and overrepresentation—in the databases remained stable or rose slightly. North Africa and West Asia increased their shares in all three sources, reducing underrepresentation. The most dominant disciplines and regions mostly displayed higher relative coverage and substantial overlap between Web of Science and Scopus.</p>