WCAG 101: Understanding the Web Content Accessibility Guidelines

The Web Content Accessibility Guidelines (WCAG) are technical standards on web accessibility developed by the World Wide Web Consortium (W3C). The guidelines represent a shared, international standard developed by many different stakeholders, including industry, disability organizations, government, and accessibility research organizations. WCAG isn’t a legal requirement, but a set of globally adopted standards. The guidelines aim to make websites, apps, electronic documents, and other digital assets accessible to people with a broad range of disabilities, including sensory, intellectual, learning and physical disabilities. 

WCAG covers a wealth of success criteria that, when followed by website designers, developers and content authors, can remove many of the barriers that people with disabilities face when navigating a website or other digital asset. Some examples include:

  • Images must contain descriptive alternative text (ALT text) so people who are blind have a description of an image that accurately conveys its meaning. 
  • The on-page text must be realizable without disrupting the way the page displays so people with vision disabilities can magnify content and have an easier time reading.
  • All form-entry tasks need to exist without a time limit or include an extended, lengthy time limit to accommodate the needs of people who need more time to fill out forms.
  • Components that exist across multiple web pages, like navigation, headers, footers, and sidebars, must consistently appear in the same places throughout the site so people always know to find them regardless of what page they’re on.
  • Users must be able to navigate your website without the use of a mouse. Users should be able to use the “tab” button on a keyboard to progress through any given page.
  • All web pages must use proper heading level structure so users with screen readers can easily navigate the site.

Who Is WCAG For?

WCAG is primarily used by web content developers (authors, designers), web authoring tool developers and web accessibility evaluation tool developers. However, understanding and conforming to the WCAG standards has become a necessity for any business or organization operating a website. If your website is not accessible, you risk legal retribution.

The Four Principles of WCAG: Perceivable, Operable, Understandable and Robust

The WCAG standards are categorized based on four main principles: perceivable, operable, understandable and robust, often referred to as POUR.


Information must be presented in a way that users can perceive it using one of their senses. In other words, a user must be able to comprehend the information presented. It can’t be blocked from all senses. Here are a few examples: 

  • Captions are provided for audio content
  • Descriptions are provided for video content
  • Content views are not restricted to a single orientation, such as landscape or portrait
  • Color is not the only way to convey information 
  • Color contrast ratio is at least 4.5:1
  • Text can be resized without loss of content or functionality


If all users can effectively navigate your website, it’s considered operable. If your site requires users to interact in a way that’s not possible for them, your website is not meeting this principle. Users must be able to interact with the components of the page, such as navigation features and the user interface. For example, people who can’t use a mouse should be able to effectively navigate your website using just the keyboard or voice controls. Examples include: 

  • All content is operable through use of a keyboard
  • A user can pause, stop or hide content that automatically moves, blinks or scrolls and lasts longer than five seconds
  • You provide users enough time to read content
  • Your pages have proper titles and proper focus order
  • The purpose of each hyperlink can be determined from the link text alone


The principle of understandable is just as it seems—users must be able to understand the information as well as understand how to operate within the user interface. This means that:

  • The language of the page is specified;
  • Labels are provided when content requires input from the user; and
  • Navigation mechanisms that are repeated on multiple pages appear in the same relevant order on each page.


Your content must be robust enough that it can be interpreted by a wide variety of possible user agents, including assistive technologies. In other words, your website should have maximum compatibility with current users as well as technologies that may evolve.

  • Elements have complete start and end tags and are nested according to their specifications
  • The name and role of all user interface components can be programmatically determined

WCAG Versions 1.0, 2.0, 2.1 and 2.2

Digital accessibility is an evolving journey. As technology improves and designs become more sophisticated, web accessibility standards must evolve as well. As such, the W3C is updating WCAG guidelines on a regular basis. 

Its first iteration, or WCAG 1.0 was released in May of 1999. It consisted of 14 guidelines and the A, AA, AAA conformance level hierarchy.

WCAG 2.0, published in December 2008, introduced the principles of perceivable, operable, understandable and robust and redefined the A, AA and AAA levels of conformance.

WCAG 2.1, published in June 2018, is considered an interim measure to provide updated standards reflecting advancements in digital content since the publication of 2.0. The primary differences between WCAG 2.0 and WCAG 2.1 concern mobile devices or tablets and introduced 17 new success criteria. 

WCAG 2.2 is expected to be published in 2022. WCAG 2.2 is anticipated to include new features that help make the user experience more inclusive and user friendly.

Each version is backwards compatible, meaning it covers additional guidelines without replacing previous ones. If your website and other digital assets are conformant with WCAG 2.2, then they are conformant with WCAG 2.1, and so on.

WCAG Levels of Conformance: A, AA, and AAA

WCAG guidelines are categorized by three levels of conformance: 

  • A = the lowest, or bare minimum conformance level
  • AA = the mid-range conformance level
  • AAA = the highest level of conformance

The typical goal for most website owners is AA conformance. AA is also the standard by which most legal requirements are judged. Level A is the bare minimum and is typically considered unacceptable. Level AAA is the highest possible conformance level and for some content can’t be achieved. 

WCAG and Legal Compliance

The WCAG guidelines are just that–-guidelines. WCAG offers specific guidance on how to make a website or other digital experience more accessible for more individuals. While WCAG isn’t a legal mandate, as the globally adopted set of standards for web accessibility, WCAG is often referred to in legislation and in court decisions as the benchmark for web accessibility. 

For example, Section 508 of the Rehabilitation Act of 1973 requires that federal agencies make their electronic and information technology accessible for individuals with disabilities, in compliance with WCAG 2.0 AA standards. Additionally, the Accessibility for Ontarians with Disabilities Act (AODA) states that all public websites and any web content published after January 2, 2012, must conform to WCAG 2.0 AA standards. The same is true of the Unruh Civil Rights Act and California Assembly Bill 434 (AB424), which requires state entity websites to be accessible to the general public, aligning with WCAG 2.1 Level AA Standards in addition to the requirements of Section 508. WCAG also became part of the EN 301 549, which is an accessibility standard that covers all European Information and Communication Technology.

While the Americans with Disabilities Act (ADA) does not specifically mention website accessibility, case law is on the side of accessibility advocates. Courts are increasingly ruling in favor of accessibility, citing Title III of the ADA. Title III mandates accessibility in “places of public accommodations,” and more and more, U.S. Federal Courts are interpreting places of public accommodations to apply to the internet, again, based on the global standards established in WCAG.

Evaluating Based on WCAG Success Criteria

There are a multitude of web accessibility evaluation tools to help you get started in determining whether your web content conforms with WCAG standards. One example is the WAVE tool. Simply type in your URL, and you’re given a summary of errors present on that page. Another is the IBM Equal Access Accessibility Checker, which lets you complete page-level testing on Chrome and Firefox browsers.

However, it’s important to understand that these tools rely solely on automation, which cannot detect every error. Automated tests can only evaluate against 25-30% of WCAG success criteria. Human testing is necessary for a truly comprehensive assessment of your digital assets’ usability and accessibility.