What are the three types of guidance provided in WCAG 2.1?

The correct answer identifies the three types of guidance provided in WCAG 2.1 as sufficient techniques, advisory techniques, and failures.

Sufficient techniques are those methods that, when implemented, are known to meet the requirements of the Web Content Accessibility Guidelines (WCAG). These techniques are evidence-based and provide a reliable means of achieving accessibility compliance.

Advisory techniques are recommendations or best practices that may improve accessibility but are not guaranteed to meet the success criteria. Though advisable, following these does not alone ensure compliance with WCAG, as they might not directly correlate with the requirements outlined in the guidelines.

Failures, on the other hand, document common errors or practices that do not meet the WCAG criteria. By highlighting these failures, the guide helps web developers recognize pitfalls that need to be avoided to ensure that their content is truly accessible.

This structure provides a comprehensive framework for understanding how to design web content that is accessible to people with disabilities, making it essential for developers and designers aiming to create inclusive digital environments.