There are a few different international standards of accessibility in technology. WCAG, Section 508, and ETSI 301 549 are the most prominent and work well together.
Web Content Accessibility Guidelines (WCAG)
The World Wide Web Consortium (W3C) and Web Accessibility Initiative (WAI) are responsible for the creation, maintenance, and updates for the Web Content Accessibility Guidelines (WCAG). WCAG provides recommendations and success criteria to help create a more inclusive and accessible internet. The currently relies on WCAG 2.0 Level AA conformance for publicly-facing websites. The active version for WCAG is 2.1 (released in 2018). Version 2.2 was in development at the time of writing. Most legislative bodies refer to WCAG 2.0 AA as the current requirement for all website content.
WCAG is informative. However, creating and delivering accessible content goes beyond meeting WCAG criteria. Since WCAG and technology are continually evolving, checking off the list of criteria today may not address the accessibility guidelines of the future. Its best to view WCAG as a helpful resource, instead of a mandatory checklist.
WCAG can also be extrapolated to non-web information and communications technology (see Guidance on Applying WCAG 2.0 to Non-Web Information and Communications Technologies, as an example).
Other International Standards
Other international standards have been developed for public procurement or publicly funded procurement.
The (European Telecommunications Standards Institute) EN 301 549 standards, issued by the European Commission, define functional accessibility requirements that can apply to different information and communications technology (ICT) products and services. It defines accessibility needs for people with different impairments and includes WCAG requirements. The Government of Canada has developed tools to support the definition of procurement specifications aligned with ETSI EN 301 549 (for example, see the ICT accessibility requirements wizard).
Similarly, the Section 508 rule legal standards (from the US Rehabilitation Act) are utilized by American purchasers. These standards are required for many publicly-funded procurements in the United States. These standards are broadly harmonized with other standards, including the ETSI EN 301 549 standards and WCAG.
Accessibility for Ontarians with Disabilities Act
European Telecommunications Standards Institute
Information and Communications Technology