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Accessibility Best Practices


Accessibility Best Practices

“The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.”

– Tim Berners-Lee, W3C Director and inventor of the World Wide Web

The Web Content Accessibility Guidelines

The Web Content Accessibility Guidelines (WCAG) were developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a single shared standard for web content accessibility that meets the needs of individuals, organizations, and governments internationally.

WCAG are stable, referenceable technical standards. Each standard has 12-13 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. [1]

The four principles

  • Perceivable - Information and user interface components must be presentable to users in ways they can perceive.
  • Operable - User interface components and navigation must be operable.
  • Understandable - Information and the operation of the user interface must be understandable.
  • Robust - Content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies.

The testable success criteria

  • Level A - For Level A conformance (the minimum level of conformance), the Web page satisfies all the Level A Success Criteria, or a conforming alternate version is provided.
  • Level AA - For Level AA conformance, the Web page satisfies all the Level A and Level AA Success Criteria, or a Level AA conforming alternate version is provided.
  • Level AAA - For Level AAA conformance, the Web page satisfies all the Level A, Level AA and Level AAA Success Criteria, or a Level AAA conforming alternate version is provided.
    • ***It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.***

This guide does not attempt to cover all of the guidelines for each principle. Nor does it attempt to highlight each level of success for each guideline. It is merely a list of Best Practices.

Quick Guide

Best Practices Quick Reference

The information found in this section is a quick reference that can be helpful when creating online materials. This quick reference does not provide tips, examples, or additional readings. Please review the available tabs for detailed information about each guideline.

Text Alternatives:

Any image included in your online content should include Alternative Text or a Null Tag.

  • Alt Text is a text-based description of the image. Information presented in the Alt Text is dependent upon the image; however, in general, it should be concise but specific. An easy idea to remember is - think about how you would describe the image to someone over the phone.
  •  A Null Tag (or Empty Tag) is used when the image is purely decorative - meaning that the image is used for page decoration or spacing. It also means that a user would not miss anything if the image were not included.

Captions & Transcripts:

Any audio, video, or audio-video content included must include Captions (and possibly a Transcript).

  • Captions provide a text version of media that is synchronized with the audio or video track. Adding captions will meet minimum accessibility guidelines.
    • Note: Some programs, like YouTube, have the ability to automatically add captions. However, because these auto-generated captions often contain errors that alter the meaning of the content, they will not meet minimum accessibility standards. Instead, use these captions as a starting point and then edit them for spelling, grammar, and content.
  • Transcripts do not have to be synced with an audio or video track. Instead, they can be downloaded and viewed as a separate file. Adding transcripts is not necessary for minimum guideline requirements, but they are useful to users that use screen readers or Braille displays.


Users must be able to separate the foreground from the background of your content, this is accomplished through careful usage of color. Also, because users may need to increase the size and contrast of the page, the text should not be presented as an image. 

  • The usage of color cannot be the only way of visually conveying information. For instance, in a form, a required field cannot only be highlighted in red. It must also contain some form of text also indicating it is required, like "Required" or an Asterisk (*).  
  • The foreground and background colors on your site must meet contrast minimums with text and images. A great website that allows you to check if your site meets contrast requirements is WebAIM's Contrast Checker.
  • Images of text should not be used if the same information could be conveyed through formatted text alone.


Use proper Content Markup so that users can navigate your site (or document).

  • Content Markup items are the tags used to style your online content. One of the most useful items is the Heading tag. Using this tag will allow users to easily navigate through the various sections of your content.
  • Although all of these criteria are useful when creating documents in programs such as Word, Docs, or Acrobat, remember to use headings is often overlooked. Use the Styles options in Word and Docs (or Bookmarks in Acrobat) to create accessible documents that allow users to jump through an outline of the paper. Not only does this make the document more accessible, but it also enhances the usability for everyone!
  • Another important item to note in this category is the Hyperlink tag. Hyperlink tags (and coding found within the tag) are separate from what users will see on the page; however, the link text that is found between the tags (<a>...</a>) should provide information about the destination whenever possible. Avoid ambiguous link text such as “Click Here”, “More”, “Link”, etc.