Skip to main content

Distance Learning | School of Professional Studies | Northwestern University

What is Web Accessibility?

For people without disabilities, accessibility is something that seems to exist on the periphery of their experiences. Closed captions on movies, wheelchair ramps into buildings, and Braille on signs are all things that non-disabled people may notice, but not often interact with. For people with disabilities, however, these tools are what allow them to fully engage with the world. And this is just as true in the digital world as the physical one. Accessibility on the internet is a vast, complicated field, requiring non-disabled designers to consider ways of experiencing the internet that may be completely unfamiliar to them. Screen reader software reads digital content out loud, keyboard navigation allows for computer interaction without a mouse, interactive transcripts highlight text along with speech: millions of people use the internet by relying on these tools. Yet many designers and developers have never considered them. Failure to design for these tools and alternate ways of interacting leads to inaccessible content, which means that large populations of users may be unable to engage with the information being shared.

WCAG 2.0

The World Wide Web Consortium (W3C) has established guidelines for making web content accessible. The “Web Content Accessibility Guidelines (WCAG 2.0) covers a wide range of recommendations for making Web content more accessible. Following these guidelines will make content accessible to a wider range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive limitations, limited movement, speech disabilities, photosensitivity and combinations of these. Following these guidelines will also often make your Web content more usable to users in general.” (W3C, 2008)

Accessibility Categories

The Guidelines are also divided into four categories, each relating to a principle of accessibility: Perceivable, Operable, Understandable, and Robust.

  • Perceivable means simply that the information presented can be perceived by the user. Although this is a seemingly obvious concept, when you begin to consider different ways of perceiving–through screen reader software, via sign language, with limited color–this principle becomes far more involved.
  • Operable means that the user can fully interact with the content through whatever tools they use. Some users are unable to use a mouse and rely on keyboard controls to navigate.
  • Understandable means that users can understand the information presented. This relates to not only the clarity and quality of writing and images, but also to the presence of alternate ways of representing the information. Text can be supported by graphics, audio, video, and more. Providing multiple avenues to the content increases understanding.
  • For a site to be Robust means that it is compatible with a variety of technologies and methods of access. This can mean different web browsers, mobile devices, and assistive technologies like screen readers.

Assistive Technologies

Many disabled people use various assistive technologies in order to navigate the Internet, and much of web accessibility is built around making sure websites are compatible with those tools. The following are a few of the most commonly used assistive technologies.

Screen Readers

Screen reader software converts digital text into a synthesized voice that reads the information on a screen to a user. Put another way, it’s a translator–taking visual communication and translating it into audio. Blind and low-vision users can thus interact with primarily visually mediums independently, rather than being forced to rely on another person to read everything out loud to them. The way that screen readers present information is somewhat different than how sighted users experience it. First, while sighted users can experience an entire page in a glance, perceiving the layout, structure, artistic choices, etc., screen reader software is much more linear. “The linear progression through the content from beginning to end is somewhat like automated telephone menu systems which do not reveal all of the options at once. Users must progress through such systems in a step-wise manner.” (WebAIM, Designing for Screen Readers) That said, there are ways for users to skim through content, using properly formatted headings and descriptive links.

Second, screen readers rely entirely on the text of a page. A screen reader cannot “see” an image in order to describe it to the user. The only information that the software will have about an image is the provided alt text. Good alt text provides the user with a brief, informative description of an image that the screen reader can rely to them. However, in many websites, the alt text consists of a file name or doesn’t exist at all. WebAIM has an excellent overview of the ways screen readers read content. If you’re interested in experiencing a screen reader for yourself, there are a few free options available. Mac OS comes with VoiceOver, Windows 10 comes with Narrator, while Windows and Mac users can both download NVDA.

Keyboard navigation

For many people, using a mouse to navigate on a computer is so second-nature that it’s done without thought. But for people with visual or mobility disabilities, using a mouse may not be an option. These users find it easier to navigate via keyboard controls. Keyboard navigation is available to everyone–hit Tab a few times to see how it works. The cursor selects every clickable link (and, with a screen reader, would read those links out loud as they were selected). A well-designed site will allow users to navigate completely through the site through use of keyboard controls.


Captions are one of the most well-known assistive technologies. They’re an option on every DVD and Blu-ray, and they can often be seen on live broadcasts aired in noisy restaurants or airports. And, like screen readers, they’re translators, converting an audio medium into a visual one. Quality captions should be synchronized to the audio, convey equivalent information, and be accessible to those who need them. Captions are different from subtitles. Subtitles convey only speech, while captions include all relevant audio, including music and sound effects. In general, accessible web design uses captions, as they provide a more complete experience for deaf and hard-of-hearing users.

Magnification/color contrast adjustment

Users with colorblindness or low vision often adjust the color contrast or the size of the display. Most operating systems and browsers allow users to make these changes on their own computers, but poorly designed websites can interfere with these adjustments. High contrast design--such as black text on white background--is preferred for ease of reading for all users.

Additional Resources

    A general resource for web accessibility, written for laypeople who might not have in-depth technical knowledge of computers, coding, or programming.
  • Do’s and don’ts on designing for accessibility
    A series of posters, created by a designer with the UK Government Digital Service, explaining best practices for design considerations for a number of disabilities (including learning disabilities, anxiety, deaf or hard-of-hearing, and blind or low vision).
  • Teach Access
    An organization that advocates for accessibility skills to become a core component of all technology and design education.
  • Association on Higher Education and Disability (AHEAD)
    A professional organization with a commitment to “equity for persons with disabilities in higher education.”