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Information and user interface components must be presentable to users in ways they can perceive.
The Perceivable principle ensures that all users can perceive the information being presented. This means that information cannot be invisible to all of their senses. Users must be able to perceive the information that is being presented, regardless of which senses they use. This principle addresses the needs of users who are blind, have low vision, are deaf, hard of hearing, or have other sensory disabilities.
If users cannot perceive content, they cannot use it. This principle is fundamental because perception is the first step in accessing information. Without perceivable content, users with disabilities are completely excluded from the experience. For example, a blind user cannot see images, a deaf user cannot hear audio, and a user with low vision may not be able to read small text or distinguish colors.
Impact: According to the World Health Organization, over 2.2 billion people have a vision impairment, and 1.5 billion people have some degree of hearing loss. Making content perceivable is essential for this significant portion of the global population.
Providing alt text for images so screen readers can describe them
Adding captions to videos for deaf and hard of hearing users
Ensuring text has sufficient contrast (4.5:1 for normal text, 3:1 for large text)
Using semantic HTML so content structure is programmatically determinable
Providing audio descriptions for video content
Making sure information isn't conveyed by color alone