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WCAG stands for Web Content Accessibility Guidelines.

Four main layers of guidance that underpin WCAG principles#

Principles: - Perceivable, Operable, Understandable, and Robust

Perceivable: – Information and user interface components must be presentable to users in ways that they can perceive. (It can't be invisible to all of their senses.)

Operable – User interface components and navigation must be operable. Users must be able to operate with the interface (the interface cannot require interaction that a user cannot perform)

Understandable – Information and the operation of user interface must be understandable. Users must be able to understand the information as well as the operation of the user interface (content cannot be beyond their understanding)

Robust – Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies. Users must have access to the content as technologies advance. (as technology advances, the content should remain accessible)


Ensure content is directly accessible to as many people as possible, and capable of being represented in different forms to match different peoples sensory, physical and connive abilities.

Success Criteria#

- Provide text alternatives for non-text content
- Provide alternatives for time based media
- Create content that can be presented in different ways, for example simpler layout. Without losing information or structure.
- Easier for users to see and hear content including separating foreground form background.
- Make all functionality available from a keyboard
- Provide users with enough time to read and use content
- Do not design content in a way that is known to cause seizures or physical reactions
- Provide ways to help users navigate, find content, and determine where they are.
- Make it easier for users to operate functionally through various inputs beyond keyboard
- Make content readable and understandable
- Make web pages appear and operate in predictable ways.
- Help users avoid and correct mistakes.
- Maximise compatibility with current and future user agents, including assistive technologies.

Sufficient technologies, advisory techniques and failures#

Sufficient techniques
If you use the sufficient techniques for a given criterion correctly and it is accessibility-supported for your users, you can be confident that you met the success criterion.

Advisory Techniques
Suggested ways to improve accessibility.
Often very helpful to users and may be the only way some users can access content
Advisory techniques are not designated as sufficient techniques for various reasons such as:
- They may not be sufficient to meet the full requirements of the success criteria
- They may be based on technology that is not yet stable

Things that can cause accessibility barriers.
The documented failures are useful for:
- Authors to know what to avoid
- Evaluators to use checking if content does not meet WCAG success criteria.