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Web Accessibility Guidelines

Accessible Design
web developer, accessibility

What Are the Four Major Categories of Accessibility?

The Web Content Accessibility Guidelines (WCAG) are a vital tool for businesses and organizations striving to make their digital content accessible to all people. The WCAG is a step-by-step set of technical requirements that cover how to make your website, app or other digital assets accessible to people with a variety of disabilities.

The guidelines cover accessibility barriers and what to look for when reviewing your website, app and digital documents. Most importantly, by following the WCAG your business complies with almost all federal, state, or local laws regarding accessibility for people with disabilities.

Understanding the Four Principles of Accessibility

The guidelines, as well as the success criteria they lay out, are organized around the following four principles. These create the foundation necessary for anyone to access and use web content. The content must be:

  • Perceivable - Information and user interface components must be presentable to users in ways they can perceive.
    • Ask yourself: Is there anything on your website that a deaf, blind, low vision or color-blind user would not be able to perceive?
  • Operable - User interface components and navigation must be operable.
    • Ask yourself: Can all functions of your website be performed with a keyboard? Can users control the interactive elements of the site? Does your website make completing tasks easy?
  • Understandable - Information and the operation of user interface must be understandable.
    • Is all of the text on your website clearly written? Are all of the interactions clear and easy to understand?
  • Robust - Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
    • Does your website only support the newest browsers or operating systems? Is the site developed with best practices? If any of these are not true, users with disabilities will not be able to use it. 


Beginning at the most basic level, your website users must be able to process information. Any information that is not presented in a processable format is simply not accessible. Among other affordances (prompts that help determine how an object can be used), this means providing audio for those that can’t see, and text for those who can’t hear.  This does not mean you have to create audio for all text on your site, but content must be consumable by screen readers and other assistive technologies. If your website or app requires sight or hearing, it won’t pass the test of perceivability.


People with disabilities must be able to operate your website with a variety of tools. Many times, users with disabilities can’t operate a mouse, and alternatives like keyboard-based operation should be used.

To help users with cognitive disabilities work your website, any animations and media should be controllable. If you have time limits for completing an action, they should be generous or customizable. Most importantly, websites and apps should be forgiving; all people, not just those with disabilities, make mistakes. Offer clear instructions, second chances, cancellation options, alerts, and warnings to help all your site users.


If users can perceive and operate your website, that doesn’t automatically mean they can understand it. Understandable websites use clear, concise language and provide functionality that is easy to follow. If a user takes an action, the correlation between the action and the result should be obvious. Navigation should be consistent across your entire site. Forms should follow a logical flow and provide clear labels, descriptions, and obvious indicators if a field is required. If your users have to go through a process, like an ecommerce checkout, suitable guidance should be provided. If this feels more like usability than accessibility, it’s because usable websites are fundamentally more accessible.


Your website users can pick their own mix of technologies. Within limits, your site should function well-enough across browsers and devices to account for personal choice and user need. While your site visitors cannot expect your site to support the very first version of Internet Explorer, it should not dictate the technology users can use. If you are doing so, you’re restricting access for any non-conforming user. Following development standards and conventions is one of the best ways to satisfy the principle of robustness. At Provisio, we follow these standards and best practices, and know that clean code is usually more robust and therefore more consumable across platforms.

Why Do Web Content Accessibility Guidelines Matter?

The WCAG is developed by a working group of experts from around the world, and it has been universally accepted and adopted.

These guidelines take the guesswork out of accessibility for developers and business owners. Because they exist, there is expert support every step of the way to make your websites usable by everyone, regardless of ability. Imagine if you pulled up your current website and said, “I need to make sure all people with disabilities can use this.” There’s no way you’d be able to anticipate every accessibility barrier on your own. At Provisio, we follow the WCAG to ensure your site is usable by all visitors and that any barriers to accessibility are addressed. We take the guesswork out of creating accessible sites to take your business further, faster. Interested in an accessibility review of your current site? Let’s connect!