The properties of illuminance meters and luminance meters are characterized by a number of selected quality indices defined in ISO/CIE 19476:2014 "Characterization of the Performance of Illuminance Meters and Luminance Meters", previously published as CIE S 023:2013. CIE 231:2019 summarizes existing national and regional classification systems of illuminance meters and luminance meters and recommends a CIE classification system. Like existing systems, the proposed CIE classification system is based on limit values for the different indices; but differently to all existing systems, the uncertainty of the determination of the quality indices is explicitly considered in the classification. In the annex some application-related requirements are recommended that should be considered where appropriate. The CIE classification system attributes a class to each quality index from 4* down to 1*, where 4* is the best quality. The lowest class of all quality indices specifies the class of the instrument. It is the first internationally agreed classification system for photometric measurement devices.