Reference manager Mendeley was founded in 2007 and bought by Elsevier in 2013. This article examines the use of the reference manager Mendeley as a citation database. It analyses the literature in which different citation indices are compared with the Mendeley citation count. The Mendeley ciation count is primarily an altmetric citation index, which takes its data from various sources and considers books, book contributions and conference papers in addition to well covered journal articles. Citation measurement is still the gold standard, but information from the Mendeley citation count is increasingly being taken into account.