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WAI - WCAG 2.0

These guidelines explain how to make Web content accessible to people with disabilities. The guidelines are intended for all Web content developers (page authors and site designers). The primary goal of these guidelines is to promote accessibility. However, following them will also make Web content more available to all users, whatever user agent they are using (e.g., desktop browser, voice browser, mobile phone, automobile-based personal computer, etc.) or constraints they may be operating under (e.g., noisy surroundings, under- or over-illuminated rooms, in a hands-free environment, etc.). Following these guidelines will also help people find information on the Web more quickly. These guidelines do not discourage content developers from using images, video, etc., but rather explain how to make multimedia content more accessible to a wide audience.


WCAG 2.0

The Web Content Accessibility Guidelines (WCAG) 2.0 is the result of a long development process that ended on 11th December 2008 with its release as a W3C Recommendation. The new guidelines represent a very important step towards new ways of developing accessible web content, including the use of recent technologies not allowed in previous versions, and being ready for future technologies yet to be invented.

WCAG 2.0 was published on 11 December 2008. WCAG 2.0 applies broadly to more advanced technologies; is easier to use and understand; and is more precisely testable with automated testing and human evaluation.

W3C WAI recommends using WCAG 2.0, instead of WCAG 1.0.

Most Web sites that conform to WCAG 1.0 will not require significant changes in order to conform to WCAG 2.0, and some may not need any changes.

WCAG 2.0 has 12 guidelines that are organized under 4 principles: perceivable, operable, understandable, and robust. For each guideline, there are testable success criteria, which are at three levels: A, AA, and AAA.


Basic principles and guidelines of WCAG 2.0

Principle 1: Perceivable

Information and user interface components must be presentable to users in ways they can perceive

This principle includes four guidelines:

  • Guideline 1.1. 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.
  • Guideline 1.2. Time-based media: provide alternative for time-based media.
  • Guideline 1.3. Adaptable: create content that can be presented in different ways (for example simpler layout) without losing information or structure.
  • Guideline 1.4. Distinguishable: make it easier for users to see and hear content including separation foreground from background.



Principle 2: Operable

User interface components and navigation must be operable.

This principle includes 4 guidelines:

  • Guideline 2.1. Keyboard accessible: make all functionality available from a keyboard.
  • Guideline 2.2. Enough time: provide users enough time to read and use content.
  • Guideline 2.3. Seizures: do not design content in a way that is known to cause seizures.
  • Guideline 2.4. Navigable: provide ways to help users navigate, find content, and determine where they are.



Principle 3: Understandable

Information and the operation of user interface must be understandable.

This principle includes 3 guidelines:

  • Guideline 3.1. Readable: make text content readable and understandable.
  • Guideline 3.2. Predictable: make web pages appear and operate in predictable ways.
  • Guideline 3.3. Input assistance: help users avoid and correct mistakes.



Principle 4: Robust

This principle only includes one guideline:

  • Guideline 4.1. Compatible: maximize compatibility with current and future user agents, including assistive technologies.



WCAG 2.0 Conformance

In order to comply with WCAG 2.0, there are some important requirements that must be met before proceeding to evaluate compliance with the success criteria. These requirements set out a basic framework: conformance levels, scope, technologies and accessible uses.

Conformance requirements

The five conformance requirements are:

  1. Conformance Level: defines the meaning of levels (A, AA, AAA) and how to achieve conformance.
  2. Fullpages: defines what is considered a ‘web page’ and where to place alternatives for non-accessible content; note that, while non-conforming content in WCAG 1.0 requires a separate alternative page, in version 2.0 the alternative can be part of the same pag
  3. Complete processes: defines the concept of ‘process’ (task) and how it affects to conformance of single web pages within the process
  4. Only accessibility-supported ways of using technologies: refers to the uses of technologies that are relied upon and the need of alternatives when these uses are not accessible.
  5. Non-interference: how non-accessible content can interfere with or prevent access to other content that would otherwise be accessible.



Differences between WCAG 1.0 and WCAG 2.0

The new WCAG 2.0 guidelines have a similar structure to those in WCAG 1.0, but there are notable differences:

  • In the first place, the guidelines are organised around four basic principles (Perceivable, Operable, Understandable and Robust), which together constitute the basic philosophy of the guideline
  • The guidelines themselves are under the principles; the guidelines also have a general character, though they refer to specific aspects of each basic principle.
  • Finally, each guideline includes a series of success criteria which, like the WCAG 1.0 checkpoints, define rules for the accessibility of Web content, but which, unlike WCAG 1.0, are testable. The success criteria are assigned conformance levels (A, AA, AAA), in a similar way as WCAG 1.0 checkpoints (although the concept of “priorities” has been eliminated); also, the same success criterion can appear several times but with slight differences for different conformance levels. The guidelines are written to be independent of the technology used to create the content, and the success criteria are aimed to be testable without ambiguity, using an automated evaluation tool or by a person. Each success criterion includes a link to the corresponding section in the rest of the supporting documents.Also, each success criterion may link to various techniques, which can be of two types:
    • Sufficient techniques: If the technique is followed, the success criterion is met by any element that uses it. 
    • Additional techniques: help to improve accessibility, but they do not ensure complete fulfilment of the success criterion. The techniques are not normative or mandatory; they only compile some known recommendations and solutions adapted to various existing technologies, but they are not the only possible solutions. They also give references to common failures (techniques to avoid) and bad practices that are known to provoke non-conformities that lead to accessibility barriers.

Guidelines and references

 The WCAG 2.0 supporting technical materials include:

  • How to Meet WCAG 2.0: A customizable quick reference to Web Content Accessibility Guidelines 2.0 requirements (success criteria) and techniques
  • Understanding WCAG 2.0: has additional guidance on learning and implementing WCAG 2.0 for people who want to understand the guidelines and success criteria more thoroughly.
  • Techniques for WCAG 2.0: gives you specific details on how to develop accessible Web content, such as HTML code examples.


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