The evaluation of research outputs in the form of journal articles is important to help with monitoring performance and to allocate funds. Elsevier's Scopus and Clarivate's Web of Science (WoS) are the two main sources for identifying outputs. For non-English-speaking countries, it is especially important that most of the scientific activity evaluated is represented in the bibliometric database used. All documents published in Scopus and WoS during 2018 (6,094,079 documents) were therefore analysed and compared for their languages and research areas. The most comprehensive source for each language and research area were identified and some coverage problems have been found.