Understanding the WCAG 2.0 Guidelines/Requirements

Graphic picture of WCAG 2.0 guidelines

The Web Content Accessibility Guidelines (WCAG) 2.0 offers practical recommendations to improve the accessibility of web content. By following these guidelines, content becomes accessible to a wider audience, including individuals with disabilities like visual impairments, hearing impairments, and learning disabilities. Adhering to WCAG 2.0 often results in better usability for all users.

WCAG 2.0 provides clear success criteria that are not tied to specific technologies. Additional guidance on meeting these criteria and general interpretation assistance can be found in separate documentation. For an overview and access to resources related to WCAG, refer to the Web Content Accessibility Guidelines (WCAG) Overview.

WCAG 2.0 builds upon the foundation established by Web Content Accessibility Guidelines 1.0 (WCAG 1.0), initially published in May 1999 as a W3C Recommendation. While conforming to either WCAG 1.0 or WCAG 2.0 (or both) is acceptable, it’s recommended to adopt WCAG 2.0 for new and updated content. Additionally, aligning web accessibility policies with WCAG 2.0 standards is encouraged.


What is in WCAG 2.0?

The Web Content Accessibility Guidelines (WCAG) 2.0 consists of 12 guidelines, grouped into four main principles: perceivable, operable, understandable, and robust.

Each guideline includes testable success criteria, categorized into three levels: A, AA, and AAA, indicating different levels of accessibility standards.

Meeting the success criteria is necessary for conforming to WCAG. In other words, content must fulfill these criteria to comply with WCAG standards.


WCAG 2.0 Checklist / Guidelines:

Principle 1: Perceivable

To ensure accessibility, information, and user interface components should be presented in a way that users can understand easily.

Guideline 1.1 Text Alternatives

It’s important to provide text alternatives for any non-text content so that users can access information in different formats, such as large print, braille, speech, symbols, or simpler language.

1.1.1 Non-text Content

All non-text content presented to users must have a text alternative that serves the same purpose, with a few exceptions outlined below:

  • Controls and Input: Non-text content used as controls or accepting user input should have a name that describes what it does.
  • Time-Based Media: For time-based media, text alternatives should give a description of the content.
  • Tests: Text alternatives for non-text content used in tests or exercises should describe what it is.
  • Sensory Experience: If non-text content is mainly meant to create a sensory experience, text alternatives should describe it.
  • CAPTCHA: For non-text content used to confirm human interaction, text alternatives explaining its purpose must be provided. Different CAPTCHA methods for various disabilities should also be available.
  • Decoration, Formatting, and Invisible Content: Purely decorative, formatting-related, or invisible non-text content should be set up so that assistive technology can overlook it.


Guideline 1.2 Time-based Media: Providing Options for Time-based Media

1.2.1 Audio-only and Video-only (Prerecorded):

When dealing with prerecorded audio-only or prerecorded video-only media, remember the following conditions apply, unless the audio or video serves as an alternative for text and is clearly identified as such: (Level A)

  • For prerecorded audio content:  Make your audio accessible by providing a text transcript. This transcript should accurately capture the spoken information, including any important details or sequence of events. Having a transcript allows people who are deaf or hard of hearing, or those who prefer to read the information, to easily understand the content.
  • For prerecorded video content:  Enhance your video’s accessibility by offering either a text transcript or an audio description. A text transcript captures the dialogue and important sounds within the video, while an audio description provides spoken commentary that describes the key visual elements on screen. This ensures everyone can enjoy your video, regardless of their visual abilities.

1.2.2 Captions (Prerecorded):

Remember to include captions for all prerecorded audio content in synchronized media, unless the media is a substitute for text and is clearly marked as such. (Level A)

1.2.3 Audio Description or Media Alternative (Prerecorded):

Provide an alternative for time-based media or audio description of the prerecorded video content for synchronized media, unless the media serves as a substitute for text and is clearly identified as such. (Level A)

1.2.4 Captions (Live):

Ensure captions are provided for all live audio content in synchronized media. (Level AA)

1.2.5 Audio Description (Prerecorded):

Offer audio descriptions for all prerecorded video content in synchronized media. (Level AA)

1.2.6 Sign Language (Prerecorded):

Include sign language interpretation for all prerecorded audio content in synchronized media. (Level AAA)

1.2.7 Extended Audio Description (Prerecorded):

Provide an extended audio description for all prerecorded video content in synchronized media when pauses in foreground audio are insufficient to convey the video’s meaning. (Level AAA)

1.2.8 Media Alternative (Prerecorded):

Make sure to provide an alternative for time-based media for all prerecorded synchronized media and all prerecorded video-only media. (Level AAA)

1.2.9 Audio-only (Live):

Offer an alternative for time-based media that presents equivalent information for live audio-only content. (Level AAA)


Guideline 1.3 – Adaptability:

Make sure content stays clear and organized even when it’s presented in simpler formats.

1.3.1 – Information and Relationships:

Ensure that the way information is presented allows it to be understood programmatically or in plain text.

1.3.2 – Meaningful Sequence:

Ensure that the order in which content appears doesn’t change its meaning and that it can be read correctly by software.

1.3.3 – Sensory Characteristics:

Provide instructions for using content that doesn’t rely only on how things look or sound.


Guideline 1.4

This guideline focuses on making content clear and accessible to all users by ensuring a clear contrast between foreground and background elements.

1.4.1 Use of Color:

Color shouldn’t be the only way to share information or prompt actions. This helps users who might have trouble seeing colors to still understand the content.

1.4.2 Audio Control:

If audio plays automatically on a webpage for more than 3 seconds, users should be able to pause or stop it. They should also have the option to adjust the volume separately from their device’s volume level.

1.4.3 Contrast (Minimum):

Text and images of text should have enough contrast to be easily readable, with a ratio of at least 4.5:1. This is important for users with visual impairments.

1.4.4 Resize Text:

Users should be able to make text bigger without needing special tools, up to 200 percent, without losing any content or features. This makes it easier for people to adjust text size based on their needs.

1.4.5 Images of Text:

Whenever possible, text should be used instead of images of text to share information. But there are exceptions, like when a specific look for the text is important.

1.4.6 Contrast (Enhanced):

For better accessibility, text and images of text should have even higher contrast, with a ratio of at least 7:1 in most cases.

1.4.7 Low or No Background Audio:

Audio on a webpage should make sure that speech is easy to hear over any background sound. Users should have ways to turn off background audio or adjust its volume.

1.4.8 Visual Presentation:

Users should have options to change how the text looks, like picking colors and making sure it’s not too wide. This makes it easier for everyone to read comfortably.

1.4.9 Images of Text (No Exception):

Images of text should only be used for decoration or when the way the text looks is really important. This makes sure everyone can access the content, no matter how they’re reading it.


Accessibility Principle 2 Operability:

The user interface and navigation should be easy to use.


Guideline 2.1 Keyboard Accessibility: 

Ensure that all features can be accessed using only a keyboard.


2.1.1 Keyboard Functionality:

Users should be able to access all features using a keyboard without needing to press keys within specific timeframes, except in cases where input depends on the user’s movement path rather than just the starting and ending points. (Level A)

2.1.2 No Keyboard Traps:

Users should be able to move focus away from any component using only a keyboard, without encountering any barriers. If additional steps are required beyond standard methods, users should be informed of how to move focus away. (Level A)

2.1.3 Keyboard Accessibility (No Exceptions):

All features should be accessible via keyboard without the need for specific timing of keystrokes. (Level AAA)


Guideline 2.2: Providing Enough Time


2.2.1 Flexibility with Timing:

Make sure users have ample time to interact with content. Time limits should be adjustable to suit different needs:

  • Disable: Allow users to turn off time limits before encountering them.
  • Adjust: Let users change time limits over a wide range, at least ten times longer than the default setting.
  • Extend: Warn users before time runs out, giving them at least 20 seconds to extend the limit with simple action, like pressing the space bar. Users should be able to extend the limit at least ten times.
  • Real-time Exception: Exceptions apply when time limits are essential to real-time events, like auctions, with no other options available.
  • Essential Exception: Time limits essential to an activity, where extending them could disrupt the activity.
  • 20-Hour Exception: Time limits longer than 20 hours are exempt from standard requirements.

2.2.2 Control Over Dynamic Content: 

Users should have control over moving, blinking, scrolling, or auto-updating content:

  • Moving, Blinking, Scrolling: Provide a way to pause, stop, or hide content that starts automatically and lasts more than five seconds unless it’s crucial to the activity.
  • Auto-updating: Users should be able to pause, stop, or adjust the frequency of auto-updating content unless it’s necessary for the activity.

2.2.3 Timing Independence: 

Content shouldn’t rely on timing constraints unless necessary for non-interactive media or real-time events. (AAA)

2.2.4 User-Controlled Interruptions: 

Users should be able to delay or stop interruptions, except for emergencies. (AAA)

2.2.5 Seamless Authentication: 

After an authenticated session ends, users should be able to resume activities without losing data upon re-authentication. (AAA)


Guideline 2.3: Preventing Seizures

2.3.1 Flash Threshold Compliance: 

Ensure web content doesn’t contain flashing elements exceeding three times in any one-second interval or surpassing specified flash and red flash thresholds. (Level A)

2.3.2 Minimized Flashing: 

To prevent seizure risks, web content should avoid flashing elements occurring more than three times in any one-second period. (Level AAA)


Guideline 2.4 Navigable

Make it easy for users to navigate your interface, find the content they’re looking for, and understand their location within the application.

2.4.1 Bypass Blocks:

Users should have a way to skip over repeated content on multiple pages (Level A)

2.4.2 Page Titles:

Each web page should have a title that clearly describes its topic or purpose. (Level A)

2.4.3 Focus Order:

When users navigate through a web page in a sequence, the focus should move to components in an order that makes sense and maintains functionality. (Level A)

2.4.4 Link Purpose (In Context):

Users should be able to understand the purpose of a link just from its text or from the text and its surrounding context, unless it would be unclear to most users. (Level A)

2.4.5 Multiple Ways:

Users should have more than one method to find a particular web page within a group of pages, except in cases where the page is part of a specific process. (Level AA)

2.4.6 Headings and Labels:

Headings and labels should accurately describe the topic or purpose of the content. (Level AA)

2.4.7 Focus Visible:

When users interact with a website using a keyboard, there should be a visible indicator showing where the keyboard’s focus is. (Level AA)

2.4.8 Location:

Users should be able to easily find information about where they are within a set of web pages. (Level AAA)

2.4.9 Link Purpose (Link Only):

A mechanism should be provided to allow users to understand the purpose of each link from its text alone, unless it would be unclear to most users. (Level AAA)

2.4.10 Section Headings:

Content should be organized using clear section headings. (Level AAA)


Principle 3: Understandability

Information and user interface operations should be clear and easy to understand.


Guideline 3.1 Readability:

Ensure that text content is easy to read and understand.

3.1.1 Language Identification: 

The default language of each web page should be easily identifiable by software. (Level A)

3.1.2 Language Identification for Text Fragments: 

Software should be able to detect the language of individual sections or phrases within the content, with exceptions for proper nouns, technical terms, ambiguous words, and commonly used phrases within the surrounding context. (Level AA)

3.1.3 Definitions for Uncommon Words: 

There should be a way to provide specific definitions for unusual or specialized terms, including idioms and technical jargon. (Level AAA)

3.1.4 Abbreviation Clarification: 

There should be a way to explain the full form or meaning of abbreviations. (Level AAA)

3.1.5 Text Complexity: 

If the text requires a reading level beyond lower secondary education, excluding proper nouns and titles, an alternative version of the content should be provided that requires no more advanced reading skills. (Level AAA)

3.1.6 Pronunciation Assistance: 

There should be a way to clarify the pronunciation of words in cases where the meaning may be unclear without knowledge of the pronunciation within context. (Level AAA)


Guideline 3.2 Predictability:

Ensure that web pages behave in expected ways.


3.2.1 Focus Behavior: 

When a component receives focus, it shouldn’t cause a change in the context. (Level A)

3.2.2 Input Behavior: 

Changing the setting of any part of the interface shouldn’t automatically lead to a change in context unless the user was informed beforehand. (Level A)

3.2.3 Consistent Navigation: 

Navigational features repeated across multiple pages should maintain the same order each time, unless the user initiates a change. (Level AA)

3.2.4 Uniform Identification: 

Components with the same function across different pages should be identified consistently. (Level AA)

3.2.5 Context Changes: 

Changes in context should only happen when the user requests it, or there should be a way to disable such changes. (Level AAA)


Guideline 3.3 Input Assistance:  

Assist users to prevent and rectify mistakes.

3.3.1 Error Identification

If an input error is detected, it should be clearly identified, and the error should be described to the user. (Level A)

3.3.2 Labels or Instructions: 

Labels or instructions should be provided when user input is needed. (Level A)

3.3.3 Error Suggestions: 

If an input error is detected, and suggestions for correction are available, they should be provided to the user unless it affects security or the purpose of the content. (Level AA)

3.3.4 Error Prevention (Legal, Financial, Data): 

For web pages involving legal commitments, financial transactions, or data modification, at least one of the following should be true: (Level AA)

  • Reversible: Submissions can be reversed.
  • Checked: User-entered data is checked for errors, and users are given a chance to correct them.
  • Confirmed: Users can review, confirm, and correct information before final submission.

3.3.5 Context-sensitive Help: 

Context-sensitive help should be available. (Level AAA)

3.3.6 Error Prevention (All): 

For web pages requiring user submissions, at least one of the following should be true: (Level AAA)

  • Reversible: Submissions can be reversed.
  • Checked: User-entered data is checked for errors, and users are given a chance to correct them.
  • Confirmed: Users can review, confirm, and correct information before final submission.


Principle 4: Ensuring Content Reliability

Content should be reliable enough to be understood accurately by various user agents, including assistive technologies.


Guideline 4.1 Maximizing Compatibility: 

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

4.1.1 Parsing: 

When creating content using markup languages, ensure elements have complete start and end tags, follow nesting specifications, avoid duplicate attributes, and use unique IDs, except where specified otherwise. (Level A)

4.1.2 Name, Role, Value: 

Guarantee that all user interface components, such as form elements and links, have names and roles that can be determined programmatically. Additionally, users should be able to control settings through code. When these settings are changed, assistive technologies need to be informed. (Level A)


Closing Thoughts

Adhering to WCAG 2.0 guidelines is essential for ensuring your content is accessible to a wider audience. By following these best practices, you can remove barriers and create a more inclusive user experience. Here at Continual Engine, we understand the importance of web accessibility and we leverage our expertise to implement these guidelines throughout the process of making digital content accessible, ensuring your message reaches everyone.

Continue Reading: Understanding WCAG 2.1 Requirements


Debangku Sarma

Digital Marketing Associate
Continual Engine

Vijayshree Vethantham

Senior Vice-President, Growth & Strategy
Continual Engine US LLC

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