This chapter presents in a descriptive and visual way the evolution of accessibility metadata in educational resources, considering the different organizations and projects that contributed in investigations and establishment of standards for their implementation. The purpose is to justify the importance of its application in the optimal search of educational resources that responds to the needs and preferences of the user, considering the variability of learning and emphasizing the even greater requirements when dealing with students with disabilities. Accessibility is an issue that is developed optimally, and its adoption is increasing; however, in the area of virtual environments and digital educational resources, the use of accessibility metadata is still incipient and requires to be understood from its implementation of comprehensive manner and the suitability of its application.