This report scientifically assesses the validity, usefulness, and fitness-for-purpose of existing healthy diet metrics for population assessment for global and national monitoring. Existing healthy diet metrics were identified and critically assessed through a set of criteria for their use as global and national monitoring indicators. After comparative evaluation, three healthy diet metrics were identified as the most suitable for global and national monitoring. The report highlights strengths and weaknesses for the existing healthy diet indicators. Some may be suitable for simple data collection tools and short data collection time while other indicators may require complex quantitative dietary information, lengthy data collection time, and might need to confirm the validity in various contexts. Some of them may only capture a limited number of the sub-constructs of the construct of healthy diets. The report underlines main knowledge gap regarding the population groups for which the metrics could be used – whether these indicators were developed for a particular demographic and/or socioeconomic groups and their ability to be used for other population groups. The report also identifies key priority areas to further explore how these indicators could be used for more population groups and settings.