With increasing availability of near-complete, structured bibliographical data, the past decade has seen a rise in large-scale bibliometric studies attempting to find universal truths about the scientific communication system. However, in the search for universality, fundamental differences in knowledge production modes and the consequences for bibliometric assessment are sometimes overlooked. This article provides an overview of article and author characteristics at the level of the OECD minor and major fields of science classifications. The analysis relies on data from the full Web of Science in the period 2000–2020. The characteristics include document type, median reference age, reference list length, database coverage, article length, coauthorship, author sequence ordering, author gender, seniority, and productivity. The article reports a descriptive overview of these characteristics combined with a principal component analysis of the variance across fields. The results show that some clusters of fields allow inter-field comparisons, and assumptions about the importance of author sequence ordering, while other fields do not. The analysis shows that major OECD groups do not reflect bibliometrically relevant field differences, and that a reclustering offers a better grouping.