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Understanding Web Accessibility

Updated: Jun 22

By Erin Porter


As part of the Americans with Disabilities Act (ADA), state and local governments and businesses that are open to the public are required to make their services (including all communications and websites) accessible to people with disabilities. The Department of Justice, which enforces the ADA, does not have detailed standards for web accessibility. The DOJ instead directs state and local governments and businesses seeking to make their websites accessible to use two of the most widely used technical standards resources:

The federal government uses these standards to make sure their own websites meet ADA compliance. Meeting the standards outlined in either of these resources ensures that your website meets the accessibility compliance required by the ADA.


WCAG Standards

The Web Content Accessibility Guidelines (WCAG) are generally considered the industry standard when it comes to web accessibility. WCAG is a project by the Web Accessibility Initiative (WAI) which focuses on creating technical specifications and guidelines for making the web accessible to people with disabilities. WAI develops these standards through the World Wide Web Consortium (W3C) which develops web standards.


The WCAG standards are occasionally updated for new content or revisions, and each finalized version of the standards is assigned an incrementing number. This often appears in references to the standards as WCAG 2.1, for example.


WCAG guidelines are broken into tiered levels of accessibility compliance that go from basic compliance to full accessibility compliance with additional ideal functionality that makes it more convenient for people with disabilities to interact with a website.

WCAG has 12 guidelines that are organized into four principles of perceivable, operable, understandable, and robust.

  • Perceivable - relates to user’s ability to perceive content on the website

  • Operable - relates to user’s ability to use and navigate throughout the page and utilize assistive technologies with the page content

  • Understandable - relates to user’s ability to comprehend and interact with content

  • Robust - relates to maximizing compatibility with present and future assistive technology and tools

Each of the guidelines defined by WCAG have a series of success criteria that define three levels of accessibility compliance. These success criteria levels are Level A, AA, and AAA. A key aspect of the success criteria is that the criteria must be testable. In order for a website to meet the WCAG standards for one of the conformance levels, the website must pass the success criteria for that conformance level.


The success criteria conformance levels build upon one another so that Level A, which is the most basic level of conformance, is included in Level AA, and both Level A and Level AA are included in Level AAA. Level AAA also includes some additional conformance requirements beyond Level A and Level AA. WCAG notes that Level AAA is not a recommended level of conformance for entire websites because some of the Level AAA success criteria cannot be satisfied for all content.


Meeting Level AA success criteria is generally accepted as meeting ADA requirements for the web.

Examples of Level A Criteria

  • All non-text content (e.g. images, charts) has associated text describing it

  • Color is not used by itself to convey information (i.e. an alert can’t just be red - it needs to have some text as well to indicate what it means)

  • The page can be navigated via keyboard

Examples of Level AA Criteria

  • Content can be viewed in both portrait and landscape view (unless one particular display orientation is necessary to get the information across)

  • The color contrast ratio of items on the page is at least 4.5:1, with exceptions for large text, decorative text or text that is part of a logo (color contrast between foreground and background colors can be determined using tools like WebAIM's Contrast Checker)

  • Text can be resized up to 200 percent (without assistive technology)

Examples of Level AAA Criteria

  • The color contrast ratio of items on the page is at least 7:1, with exceptions for large text, decorative text or text that is part of a logo

  • There are warnings for the amount of time that inactivity on the site could cause the user to lose data

  • The page content is organized with headings



Testing for Web Accessibility

There are a plethora of tools and techniques for testing web accessibility depending on the level of web accessibility you want to achieve. ADA testing often requires a combination of manual and automated testing methods.


Manual testing involves testing that the success criteria described in WCAG guidelines have been met using a manual testing method, testing each criteria one at a time. Manual testing might include testing the tab order on a webpage or testing that a screen reader can correctly identify the elements on a page.


Automated testing involves using tools that test that the WCAG guidelines have been met. There are a number of browser plugins that can make it easy to test the basic accessibility of a page with the click of a button. The downside of these automated testing tools is that they may not be able to determine issues such as color contrast if there are non-visible elements on the page, and you may have to perform additional manual testing to determine if they are in fact ADA compliant. However, the automated testing tools are a great place to start and many allow you to specify the level of WCAG compliance the tool should test.


Axe DevTools browser extension is one of our favorite tools for basic automated ADA testing, but there are many automated testing tools to choose from.


Further Reading:

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