Introduction

Accessibility guidelines help make digital products usable for people with disabilities. The most prominent is the Web Content Accessibility Guidelines (WCAG), developed by the World Wide Web Consortium (W3C). Originally focused on web content, WCAG has evolved into a comprehensive framework that applies to various digital technologies—including mobile apps.

WCAG

As of 2025, WCAG 2.2 is the current standard, with WCAG 3.0 work-in-progress. The guidelines rest on four core principles (also called POUR principles):

• Perceivable: Information and interface components must be presented in ways users can perceive—it cannot be invisible to all their senses.
• Operable: Users must be able to operate interface components and navigation—the interface cannot require interactions that a user cannot perform.
• Understandable: Users must be able to comprehend both the information presented and how to operate the interface—the content or operation cannot be beyond their understanding.
• Robust: Content must be robust enough to be interpreted reliably by a wide variety of user agents, including assistive technologies. As technologies and user agents evolve, the content should remain accessible.

WCAG guidelines carry significant legal and regulatory weight beyond their technical value. Many countries have incorporated WCAG standards into accessibility laws and procurement requirements, making compliance a legal obligation (e.g., Singapore’s Digital Service Standards for governmental digital services). Organizations that provide digital services often must demonstrate conformance to specific WCAG levels to comply with disability rights legislation.

WCAG Conformance Levels

WCAG defines three conformance levels. Level A addresses basic access issues that are essential for accessibility. Level AA builds on Level A with additional requirements that significantly impact usability. Level AAA represents enhanced accessibility. Most institutions aiming to make their digital products accessible target Level AA conformance.

Level A addresses the most fundamental accessibility barriers. These criteria focus on essential features that, if missing, would make content inaccessible to certain users through assistive technology. Level A requirements must be testable through a combination of automated testing and human evaluation.

Level AA builds on Level A by addressing barriers that significantly impact usability for people with disabilities. This level is the most widely adopted standard for legal compliance and organizational policy. Level AA criteria require evaluation methods including both automated testing and human assessment to ensure content remains functional when resized, interactive elements are appropriately sized, and other usability factors are met. These requirements reflect a commitment to creating experiences that are genuinely usable by people with diverse abilities.

Level AAA represents the most stringent conformance level, incorporating enhanced accessibility features that go beyond typical requirements. While these criteria provide the best possible accessibility experience, it is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA success criteria for some content.

Types of Success Criteria

WCAG 2.2 success criteria address different aspects of accessibility to ensure content is perceivable, operable, understandable, and robust for all users. These criteria can be broadly categorized into several types based on the accessibility barriers they address:

• Structure and semantics criteria ensure that content is organized in ways that assistive technologies can programmatically determine and convey to users. These requirements focus on making information and relationships presented through visual formatting available to users who cannot perceive visual presentation. Success criteria in this category address proper use of headings, labels, page titles, and semantic markup that allows assistive technologies to understand and navigate content structure effectively.
• Keyboard accessibility criteria ensure that all functionality available through a mouse or other pointing device is also operable through a keyboard interface. These requirements are essential for users who cannot use a mouse due to motor disabilities or who rely on assistive technologies that simulate keyboard input. Success criteria address making all interactive elements keyboard-accessible, ensuring users can navigate through content without encountering keyboard traps, and providing visible focus indicators so users can track their position as they navigate.
• Visual presentation criteria address how content appears on screen to ensure it remains perceivable and usable for people with visual disabilities. These requirements cover color contrast between text and backgrounds, text resizing capabilities, and spacing that affects readability. Success criteria in this category ensure that visual design choices don't create barriers for users with low vision, color blindness, or other visual impairments, while also benefiting users in challenging viewing environments.