Free range eggs require hens to have outdoor access, but the quality of that access varies enormously. How many hens actually go outside significantly affects their welfare.
Free range certification guarantees outdoor access exists, but does not guarantee that all hens benefit from it. Hens at the back of large buildings may never go outside, missing the welfare benefits of outdoor access - foraging, dust bathing in natural substrate, and more complex environments. Range enrichment with vegetation, shelters, and varying terrain encourages more hens to range further. Some higher-tier free range systems with smaller flock sizes, more pop holes, and better range design achieve much higher ranging rates than the minimum standard.