This document lays down harmonized identifiers for marketed liquid and gaseous fuels. The requirements in this document are to complement the informational needs of users regarding the compatibility between the fuels and the vehicles that are placed on the market. The identifier is intended to be visualized at dispensers and refuelling points, on vehicles, in motor vehicle dealerships and in consumer manuals as described in this document. Marketed fuels include for example petroleum-derived fuels, synthetic fuels, biofuels, natural gas, LPG, hydrogen and biogas and blends of the aforementioned delivered to mobile applications. NOTE For the purposes of this document, the terms % (m/m) and % (V/V) are used to represent respectively the mass fraction, ¼, and the volume fraction, Æ.