SNIP, which is an abbreviation of source normalized impact per paper, is an advanced metric of the citation impact of scientific journals. The metric has been developed by CWTS. Unlike the popular journal impact factor, SNIP corrects for differences in citation practices between scientific fields. It therefore allows for much fairer comparisons between journals in different fields. SNIP is based on the Scopus database, a large multidisciplinary bibliographic database produced by Elsevier.