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Introduction to WCAG 2.x

The Web Content Accessibility Guidelines (WCAG) are web accessibility guidelines published by the Web Accessibility Initiative (WAI).

The WCAG's goal is to provide a single shared standard for web content accessibility that meets the needs of individuals, organizations and governments internationally. Over time, WCAG has produced various versions of the Web Content Accessibility Guidelines. WCAG 2.0 was published on 11 December 2008, WCAG 2.1 was published on 5 June 2018. WCAG 2.2 is a W3C working draft as of 5 June 2020.

WCAG 2.x

WCAG 2.x consists of 12 guidelines. It is organized around four principles which form the acronym "POUR". They include, but are not limited to:

1. Content must be Perceivable (P).

  • Provide a text alternative for all non-text content.
  • Provide synchronized alternatives for multimedia (such as captioned video, audio descriptions etc).
  • Information and structure must be separate from presentation.
  • Make it easy to distinguish foreground information from the background (for example: good color contrast).

2. Interfaces must be Operable (O).

  • All functionality must be operable via keyboard.
  • Provide users enough time to read and use content.
  • Do not design content in a way that is known to cause seizures.
  • Provide mechanisms for users to find content, orientate themselves and navigate through it.

3. Content and controls must be Understandable (U).

  • Make text content readable and understandable.
  • Make the placement and functionality of content predictable.
  • Help users avoid and correct mistakes.

4. Content must be Robust (R).

  • Support compatibility with current and future user agents.

Layers of guidance

The WCAG provides various ways to help authors meet its standard called "layers of guidance". They include the following :


WCAG 2.x guidelines are categorized into 3 levels of conformance in order to meet the needs of different groups and situations. Under each principle, there is a list of guidelines that addresses the principles.

Success criteria

Under each guideline, there are success criteria that describe specifically what is to be done in order to conform to the standard. Each success criteria is written as a statement that will be either true or false when specific web content is tested against it. A convenient list of the success criteria is also provided.


The techniques document provides guidance for web authors and evaluators on meeting WCAG 2.1 success criteria. A convenient list of the WCAG 2.1 techniques can be found here.

Common failures

These are common mistakes that are considered failures of Success Criteria of WCAG 2.x. A comprehensive list of WCAG 2.x common failures is also provided.

What's new?

WCAG 2.1 is the current standard. It was initiated with the aim of improving accessibility guidance for three major groups:

  • People with cognitive or learning disabilities,
  • People with low vision, and
  • People with disabilities on mobile devices.

There are additional success criteria in WCAG 2.1 that are not in WCAG 2.0. They are introduced in What’s New in WCAG 2.1. For a detailed review of WCAG 2.1 , see Web Content Accessibility Guidelines (WCAG) 2.1.

While WCAG 2.0 remains a W3C recommendation, the W3C advises the use of WCAG 2.1 in order to maximize future applicability of accessibility efforts.

In effect, the publication of WCAG 2.1 does not nullify WCAG 2.0 as content that conforms to WCAG 2.0 also conforms to WCAG 2.1.


The following are important points to remember:

  • WCAG is a set of accessibility guidelines published by WAI.
  • WCAG 2.0 and WCAG 2.1 are stable, referenceable technical standards.
  • They have 12-13 guidelines that are organized under 4 principles: perceivable, operable, understandable, and robust.
  • Content that conforms to WCAG 2.0 is also compatible with WCAG 2.1.

Further reading