chapter three

3 Make content easy to perceive

 

This chapter covers

  • Ensuring sufficient contrast for all types of content.
  • Verifying that color alone is not used to convey meaningful information.
  • Establishing accessibility requirements for images.
  • Describing accessibility requirements for audio and video content.

Think about any web app you’ve built, are currently building, or manage, and consider this question:

Can every user perceive all of your content – not just text – regardless of whether they rely on vision, hearing, or touch (such as braille)?

In the previous chapter, we looked at who benefits from accessibility and the fundamental techniques and technologies that support it. Different people have different needs, and we cannot assume everyone perceives content the same way. This chapter will examine challenges and solutions to ensure your content is perceivable by everyone. Whether your content is formatted text, images, audio, or video, it must be presented in ways that work across different sensory channels, user agents, and assistive technologies.

We'll examine common pitfalls that prevent users from perceiving content and introduce practical principles for avoiding them.

NOTE

Chapter 4 examines text content in more detail, including understandability and adaptability to people’s viewing preferences.

Let’s start by reviewing the foundational requirements for making content perceivable by everyone.

3.1 Ensure sufficient contrast

3.1.1 Measuring contrast

3.1.2 Ensure sufficient contrast in text

3.1.3 Ensure sufficient contrast in UI components and graphics

3.1.4 Ensure contrast across viewport sizes, zoom levels, and orientation

3.1.5 Respect dark and light modes

3.2 Avoid using colors alone

3.3 Use images carefully

3.3.1 Decorative images

3.3.2 Simple informative images

3.3.3 Functional images

3.3.4 Complex images

3.3.5 Interactive images (image maps)

3.4 Handle audio and video carefully

3.4.1 Do not force audio or video on people

3.4.2 Media alternatives

3.4.3 Auto-playing audio

3.4.4 Sound as feedback

3.5 Summary

3.6 References