Web Content Accessibility Guidelines

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The WCAG 2.0 is a technical standard designed by the W3C to show how to make web content that is accessible to people with disabilities.

WCAG 2.0 is based on four design principles. Each principle has a number of associated guidelines, and each guideline has testable success criteria, each of which has an associated level: A, AA or AAA.

Design Principles

WCAG 2.0 is based around four design principles that state that, in order for a website to be accessible, it must have content that is perceivable, operable, understandable and robust.

  1. Perceivable. Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to perceive the information being presented (it cannot be invisible to all of their senses).
  2. Operable. User interface components and navigation must be operable.
  3. Understandable. Information and the operation of user interface must be understandable.
  4. Robust. Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.


Each design principle has a number of guidelines associated with it. There are 12 guidelines in total.

  1. Perceivable:
    • Text alternatives. Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
    • Time-based media. Provide alternatives for time-based media.
    • Adaptable. Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
    • Distinguishable. Make it easier for users to see and hear content including separating foreground from background.
  2. Operable:
    • Keyboard accessible. Make all functionality available from a keyboard.
    • Enough time. Provide users enough time to read and use content.
    • Seizures. Do not design content in a way that is known to cause seizures.
    • Navigable. Provide ways to help users navigate, find content, and determine where they are.
  3. Understandable:
    • Readable. Make text content readable and understandable.
    • Predictable. Make Web pages appear and operate in predictable ways.
    • Input assistance. Help users avoid and correct mistakes.
  4. Robust:
    • Compatible. Maximize compatibility with current and future user agents, including assistive technologies.

(Source: WCAG 2.0 at a glance)

Success criteria

Each of the guidelines has a number of associated success criteria.

For example, Guideline 1.2, which focuses on time-based media, has nine success criteria. Success Criteria 1.2.2 states, “Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such.”

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