Behavioural assessments can be used to indicate the welfare of broiler chickens. The occurrence or frequency of certain behaviours associated with negative emotional states or inappropriate environment can indicate poor welfare. On-farm assessments can include fear or human-animal relationship tests, as well as behaviours like panting, piling, and huddling. Conversely, the occurrence or frequency of behaviours associated with positive emotional states or suitable environments can indicate improved welfare. In this case, the most common are assessing play behaviour, comfort behaviours, and exploratory behaviours. Behavioural indicators provide an important complement to other animal-based measures. However, it is important to remember that any behaviour test that relies on movement may be difficult to interpret in heavier or older broilers who are not able to move as well.