Summary of Web Content Accessibility Guidelines (WCAG) 2.0 Relevant to the Development of an Access App

Dr. Juliette Fritsch

June, 30 2017


Accessibility guidelines; WCAG2.0; best practices



What is this study about?

There are many accessibility policies out there and a confusing number of guidelines. The core set of guidelines that all web developers and programmers should pay attention to are the Web Content Accessibility Guidelines (WCAG) issued by the Web Accessibility Initiative, which are widely regarded as the international standard for web accessibility. This is a summary of the most recent version (2.0) of those guidelines. It is not comprehensive, but rather intended as an introduction to the key issues.

Top line summary

This case study introduces the guiding body and core organizational principles that direct accessibility for web developers.

About the author

Dr. Juliette Fritsch is the Principle Investigator for the Access App project and Chief of Interpretive Experiences and Creative Partnerships at the Peabody Essex Museum.


This is a summary of the extensive advice and guidance provided by the Web Content Accessibility Guidelines (WCAG) 2.0 from the Web Accessibility Initiative, a special project of the World Wide Web Consortium. It highlights elements of the guidelines most applicable for the Access App project. It does not prescribe in full detail all the steps that can and should be taken to ensure 100% accessibility.

The WCAG principles and guidelines are aimed at increasing accessibility for people with a range of disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive limitations, limited mobility, speech disabilities, photosensitivity, and combinations of these. However, the principles clearly state they are not able to address the needs of people with all types, degrees, and combinations of disability.

There are three levels of compliance: A (lowest), AA, and AAA (highest). The guidelines state that even AAA level content will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive language and learning areas.

Any Access App project should aim for certified AAA compliance—although this is very hard to achieve. The guidelines themselves underline the difficulty of achieving full AAA compliance for an entire website, versus individual pages of a website. The guidelines are divided into four principles, with specific guidance for how to treat individual elements related to each principle. To achieve AAA compliance, each element of guidance has success criteria that are rated A, AA, or AAA. I have summarized success criteria that I see as useful to the Access App; however, the full criteria do go into far more detail, such as parsing out specific elements of web pages, so if Access App producers are confused or stuck, they should refer to the WCAG 2.0 themselves. Two other useful documents to reference are Understanding WCAG 2.0 and Techniques for WCAG 2.0.

In terms of evaluating compliance, the WCAG 2.0 success criteria are written as testable statements that are not technology specific. This enables them to remain relevant as technology advances. A “conformance claim” (i.e., a claim that the technology is complying with the WCAG guidelines) may be made to cover one page of a website, a series of pages, or multiple related pages. Although conformance can only be achieved at the stated levels, authors are encouraged to report (in their claim) any progress toward meeting success criteria from all levels beyond the achieved level of conformance. When a page is part of a sequence presenting a process, all pages in the process should conform at the specified level or better. Authors of pages that cannot conform due to content outside of the author’s control may consider a Statement of Partial Conformance. This can also be used for pages that will have third-party info added or pages that will later have additional content added to them. For example, an e-mail program, a blog, an article that allows users to add comments, or applications supporting user-contributed content. Another example would be a page, such as a portal or news site, composed of content aggregated from multiple contributors, or sites that automatically insert content from other sources over time, such as when advertisements are inserted dynamically.

In these cases, it is not possible to know at the time of original posting what the uncontrolled content of the pages will be. It is important to note that the uncontrolled content can affect the accessibility of the controlled content. A determination of conformance can be made based on best knowledge. If a page of this type is monitored and repaired (nonconforming content is removed or brought into conformance) within two business days, then a determination or claim of conformance can be made because—except for errors in externally contributed content that are corrected or removed when encountered—the page conforms. No conformance claim can be made if it is not possible to monitor or correct nonconforming content.

There are four principles for conformance, each with its own set of guidelines. The guidelines provide practical examples of how to meet the principles. The principles are:

  1. Perceivable – Information and user interface components must be presentable to users in ways they can perceive.
  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.

Following are the key guidelines relating to each principle that any Access App producer should be aware of:

Principle 1: Perceivable

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

Note: because the guidelines are summarized, I have categorized them differently so there is no confusion with how they are numbered in the full WCAG information.


  1. Text alternatives should be provided 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. An exception is non-text content that is primarily intended to create a specific sensory experience, in which case text alternatives should at least provide descriptive identification of the non-text content.
  2. Alternatives should be provided for prerecorded media (labeled “time-based media” in the guidelines to distinguish it from “live-stream media”). The exception is when the audio or video is already a media alternative, for example, for text, and is clearly labeled as such.

Techniques to use include captions, audio description, media alternatives, and sign language.

The following four guidelines are especially important for any interpretive interface that museums and cultural institutions might use, because meaning is often conveyed visually through these tools.


  1. Content form and layout should be adaptable, with the possibility to be presented in different ways without losing information or structure. Any meaningful information or relationships that are conveyed through visual design, hierarchies, and sequencing, should be easy to make available in other ways.
  2. Information, structure, and relationshipsconveyed through presentation should be programmatically determined or are available in text.
  3. Ensure that a correct reading sequence can be programmatically determined for meaningful sequences, in which the order of content presentation affects meaning.
  4. Ensure that instructions provided for understanding and operating content do not rely solely on sensory characteristics, such as shape, size, visual location, orientation, or sound.

Programmatically determined means that essentially all author-supplied content should be provided in a way that different users and any tools they might use, for example, assistive technologies, can extract and present this information in different modalities. The following guidelines are for use with programmatically determined content.


Content should be distinguishable, easy for users to see and hear—for example, by separating foreground from background, making sure color is not the only

  1. means used to convey information, and audio control of any auto-play can be handed over to the user, including turning off any background sounds.
  2. Text can be resized without assistive technologyup to 200 percent without loss of content or functionality. Avoid using images of text to convey key information. Text should have a contrast ratio of at least 4.5:1, except for the following:
  • Large Text: Large-scale text, and images of large-scale text, have a contrast ratio of at least 3:1;
  • Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains other significant visual content, have no contrast requirement. Logotypes (text that is part of a logo or brand name) are considered essential.

Principle 2: Operable

User interface components and navigation must be operable.


  1. Provide users enough time to read and use content. This success criterion helps ensure that users can complete tasks without unexpected changes in content or context that are the result of a time limit. Timing should be adjustable, so for each time limit that is set by the content, at least one of the following should be true:
    Turn off: The user is allowed to turn off the time limit before encountering it; or
    Adjust: The user is allowed to adjust the time limit before encountering it over a wide range that is at least ten times the length of the default setting; or
    Extend: The user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action (e.g.,, “press the space bar”), and the user is allowed to extend the time limit at least ten times; or
    Real-time Exception: The time limit is a required part of a real-time event (e.g., an auction), and no alternative to the time limit is possible; or
    Essential Exception: The time limit is essential and extending it would invalidate the activity; or
    20 Hour Exception: The time limit is longer than 20 hours.
  2. Avoid moving, blinking, scrolling, or auto-updating essential information, except content that is updated periodically by software.
  3. Make users aware of intentional pauses, so that they know the app is not broken and that they are not missing essential information. For example, an animation that occurs as part of a preload phase or similar situation can be considered essential if interaction cannot occur during that phase for all users and if not indicating progress could confuse users or cause them to think that content was frozen or broken.
  4. Do not design content in a way that is known to cause seizures. Use the Three Flashes or Below Threshold, where elements do not contain anything that flashes more than three times in any one second period.
  5. Provide ways to help users navigate, find content, and determine where they are.
  6. Ensure a mechanism is available to bypass blocks of content that are repeated on multiple pages.
  7. Ensure headings, labels, and pages have titles that describe topic or purpose.
  8. If a page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components should receive focus in an order that preserves meaning and operability.
  9. The purpose of each link can be determined from the link text alone or from the link text together with its programmatically determined link context, except where the purpose of the link would be ambiguous to users in general.
  10. More than one way is available to locate a page within a set of pages except where it is the result of, or a step in, a process.
  11. Information about the user’s location within a set of pages is available.
  12. Section headings are used to organize the content.“Heading” is used in its general sense and includes titles and other ways to add a heading to different types of content.

Principle 3: Understandable

Information and the operation of user interface must be understandable.


  1. Make text content readable and understandable.
  2. The default human language of each page can be programmatically determined.
  3. A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon.
  4. A mechanism for identifying the expanded form or meaning of abbreviations is available.


A mechanism is available for identifying specific pronunciation of words where the meaning of the words, in context, is ambiguous without knowing the pronunciation.

  1. Pages appear and operate in predictable
  2. Navigational mechanisms that are repeated on multiple pages within a set of pages occur in a consistent relative order each time they are repeated, unless change is initiated by the user.
  3. Components that have the same functionality within a set of web pages are identified consistently.
  4. Provide input assistance to help users avoid and correct mistakes.
  5. If an input error is automatically detected, the error is identified and described to the user in text.
  6. Labels or instructions are provided when content requires user input.
  7. A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.
  8. Context-sensitive help is available.


Principle 4: Robust

Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.

Maximize compatibility with current and future user agents, including assistive technologies.


While these guidelines may feel complex and confusing, they are important to pay attention to because they are the foundation of understanding how digital accessibility works.