First Steps
Laying the Foundation
Applying the Knowledge
Ending and Next Steps

The Four Principles of Digital Accessibility

There is an international consortium that is responsible to develop and promote the web (internet). It called World Wide Web Consortium or W3C.

Web Content Accessibility Guideline (WCAG)

W3C has developed a guideline that sets forward the standard of digital accessibility.  The guideline is called Web Content Accessibility Guideline (WCAG). Even though, WCAG was primary developed for setting web accessibility standards, it is equally relevant to other aspects of digital accessibility like making accessible documents.

According to WCAG, for any documents to be accessible, it needs to follow the four principles. These principles are as follows:

  • Perceivable
  • Operable
  • Understandable
  • Robust

These four principles are often together termed as POUR.

The POUR principles


All users using our documents should be able to perceive all parts of it. It means, all items used in the document or any information provided by document should be visible to all users. They can be visible in various forms. Like any image used in our document should contain proper description so that users with visual impairment can access these images. 


All users should be able to operate our document. They should be able to go to different parts of the document with ease and if the documents require any interaction from users like filling up a form or checking the box, then the users should be able to do that, by using relevant assistive technologies, if needed.


The content of the document should be written in simple language. Users with various level of learning capabilities should be able to comprehend the information provided by document. This principle is more relevant to the content creation; rather than technologies used.

This principle is more oriented to the contents of the document rather than the design. The content of the documents should be written in a simple language so that all types of users can understand the contents easily included in the documents.


The users may use different types of technologies to access on our documents. Besides common technologies like mobile, laptop and desktop, they might use audio player, E-Book reader, braille display, sign language and so on for the access. Therefore, our documents should robust enough to be compatible with all those technologies.

Summing Up

This course is fully based on the POUR principles. In coming chapters, we will discuss, how we can make our documents adhere to these principles and become accessible to all users.

Based on these four principles, the whole course of digital accessibility has been designed. We will discuss more how can we make our documents accessible based on these principles in the coming chapters.