Sunscreens are a personal care product that provides photoprotection to the skin. The protection levels of each sunscreen can be measured as sun protection factor (SPF) for UV-B and protection factor of UV-A (PA) for UV-A. In order to provide protection, UV filters are needed. UV filters can be organic or inorganic, but both possess different mechanisms of function. They are also employed in combination to provide a wider range of protection; however, their overuse may cause problems for both consumers and the environment. Therefore, SPF boosters play a pivotal role in increasing the level of protection while maintaining or even enhancing protection with minimal incorporation of UV filters. The aim of this chapter is to discuss the functions, roles, and effectiveness of each SPF booster categorized into seven groups according to their mode of actions, which are film formers, scattering particles, emollients, antioxidants, rheology modifiers, emulsifiers, and photostabilizers. The boosters themselves do not have an effect on SPF. However, when the boosters are formulated with UV filters, the protection will increase. In summary, scattering particles and emollients are the most effective classes in terms of SPF enhancement as they both can provide higher SPF with low UV filter concentrations and can be used with both organic and inorganic UV filters.