Core Principles of Digital Accessibility

Digital Accessibility Principles

Mines’ Electronic and Information Technology Accessibility Policy uses the Web Content Accessibility Guidelines (WCAG) version 2.1, Level AA as the standard for accessible web content at the Colorado School of Mines.

WCAG lists four principles to consider when making websites and digital content accessible to as many people as possible. These principles are that digital content must be perceivable, operable, understandable, and robust to as many users as possible. Read on to learn more about the principles or visit the web accessibility guidelines for tips on meeting WCAG guidelines.

Colorado School of Mines student working with a digital map of the United States


Perceivable means that a web resource offers more than one way for users to perceive its content with their senses. For example, visual information in a video would also be described in an audio track, or images would have an accompanying text description that can be read aloud by assistive technology. A key part of perceivability is offering users options, such as options to enable captions or to transform documents into different formats. Read more about perceivable content at WebAIM.


Operable means that users can use a variety of different devices beyond a standard mouse and keyboard to interact with a website, and that mobile websites and apps with touch interactions support alternatives for people with limited mobility. Keyboard functionality is particularly important for users who use assistive technology such as screen reader software.

Operability also includes giving people control over their experience of a website’s content. This includes removing time limits as much as possible; being able to turn off sound, video, or animations; and recognizing error messages and having a chance to correct errors in forms. Read more about operable content at WebAIM.


Understandable means that content is written in language that is as clear and simple as possible. Content at Colorado School of Mines is likely to include complex technical and scientific information, which makes it even more important to write clearly, avoid jargon, and explain acronyms or abbreviations. Understandable content is also easy to navigate and has a consistent, logical structure. Read more about understandable content at WebAIM.


Robust means that content is developed according to current standards and best practices in order to make it usable on as many platforms and devices as possible. This includes creating valid HTML, following the Web Content Accessibility Guidelines, and avoiding technology such as accessibility overlays that make automated modifications to the code of a website and may interfere with users’ assistive technology. Read more about robust content at WebAIM.