More than just a scientific curiosity, the light emitted by a flame can be recorded and analysed to infer many of the flame’s important features. There are numerous applications in research laboratories and practical combustion devices. Emission of light from a flame, oftentimes referred to as chemiluminescence or spontaneous emission, has been studied extensively for conventional hydrocarbon fuels, such as methane or natural gas, and is well understood. This cannot be said for flames including ammonia in the fuel. In this presentation, the current knowledge – and its limits – on the light signature of ammonia flames will be reviewed. Recent experiments conducted at KAUST and providing more insights into the rich light signature of ammonia flames will also be discussed and future practical applications of optical flame sensors will be outlined.