The Web Accessibility Directive is a European Union Directive that is aimed at improving the accessibility of public sector websites and mobile applications.
European Union member states were required to ensure that their public sector websites were compliant with the Directive by September 23, 2018. Mobile applications had a later deadline, set for June 23, 2021.
Each member state has to have its own legislation that implements the Web Accessibility Directive. In Finland, we have the Act on the provision of digital services (digital services act).
You can read a bit more general information about the Web Accessibility Directive on the A11ying with Sanna main site: I would if I could.