The use of artificial light at night in the outdoor environment may introduce negative andunwanted side-effects such as light pollution and unwanted impacts on humans, ecosystemsand biodiversity. Therefore, appropriate measures for reducing the adverse effects of artificiallight at night are important to establish a sustainable use of outdoor lighting. This paperpresents an updated overview and a state-of-the-art of available and effective measures forreducing artificial light at night, which range from strategical and high-level recommendationsto more practical and applicable lighting design recommendations and principles. Another aimis to identify prioritized future research questions and areas that will enhance progress withinthe area. We present the current recommendations into three groups: (I) recommendations forlegislation at the national or international levels, (II) recommendations for technical andpractical adaptations of the lighting design and (III) recommendations for sensitive species,taxa, areas or ecosystems.