Intro to Accessibility Accessibility Principles

Learning objective: By the end of this lesson students will be able to apply the four core principles of accessibility — perceivable, operable, understandable, and robust.

The four principles of accessibility

The accommodations we’ve discussed help our content adhere to the four main accessibility principles. These principles state that content should be perceivable, operable, understandable, and robust.

Perceivable

Information and user interface components must be presented so all users can perceive them. We do this through a few methods, namely:

• Provide text alternatives so that content can be made into text.
• Design for adaptability - our content should be able to be presented differently without losing any important information or structure.

Operable

User interface components and controls must be operable by all users.

• Content should be keyboard accessible.
• Refrain from adding content that can trigger photosensitive conditions like epilepsy.
• Allow for different input modalities, such as touch.

Understandable

Information and the operation of user interface components must be understandable. For example:

• Content should be readable and presented in a predictable way. Instructions should be clear and concise.
• Design our sites to assist users in inputting information so that they can avoid and correct mistakes when they enter information we weren’t expecting.

Robust

Content must be robust enough to be interpreted reliably by users, including the assistive technologies they may use.

• We should design our website to be compatible with as many different browsers and assistive technologies as possible.