# Standards
The World Wide Web Consortium (W3C) Web Accessibility Initiative (WAI) develops web accessibility standards for the different components:
- User Agent Accessibility Guidelines (UAAG) (opens new window)
- web browsers and media players, including some aspects of assistive technologies
- Authoring Tool Accessibility Guidelines (ATAG) (opens new window)
- authoring tools
- Web Content Accessibility Guidelines (WCAG) (opens new window)
- web content - used by developers, authoring tools, and accessibility evaluation tools
# Web Content Accessibility Guidelines (WCAG)
WCAG 2.1 (opens new window) extends on WCAG 2.0 (opens new window) and allows implementation of new technologies by addressing changes to the web. The W3C encourages use of the most current version of WCAG when developing or updating Web accessibility policies.
# WCAG 2.1 Four Main Guiding Principles (abbreviated as POUR):
- Perceivable (opens new window)
- Users must be able to perceive the information being presented
- Operable (opens new window)
- Interface forms, controls, and navigation are operable
- Understandable (opens new window)
- Information and the operation of user interface must be understandable to all users
- Robust (opens new window)
- Users must be able to access the content as technologies advance
# Web Accessibility Initiative – Accessible Rich Internet Applications (WAI-ARIA)
W3C's WAI-ARIA provides guidance on how to build dynamic content and advanced user interface controls.