Brine systems in Europa’s ice shell have been hypothesized as potential habitats that could be more accessible than the sub-ice ocean. We model the distribution of sub-millimeter-scale brine pockets in Europa’s ice shell. Through examination of three habitability metrics (water activity, ionic strength, salinity), we determine that brine pockets are likely not geochemically prohibitive to life as we know it for the chloride and sulfate-dominated ocean compositions considered here. Brine volume fraction is introduced as a novel habitability metric to serve as a proxy for nutrient transport and recycling—because of its role in governing permeability—and used to define regions where active, dormant, and relict habitats are stable. Whereas dormant habitats could exist wherever brine is stable (bottom ~20% of a thermally conductive ice layer), active habitats are confined to meter-scale regions near ice-water interfaces where freezing is occurring. This classification scheme can help guide future life-detection missions to ocean worlds.