Complete Guide to WCAG 2.1 Success Criteria

What Are WCAG 2.1 Success Criteria?

WCAG 2.1 success criteria are a set of accessibility standards developed by the World Wide Web Consortium (W3C) to ensure digital content is usable by individuals with disabilities. 

Version 2.1 expands on WCAG 2.0 by introducing 17 new criteria focused on mobile accessibility, low vision, and cognitive impairments.

In total, WCAG 2.1 includes 78 success criteria grouped under three conformance levels:

• Level A: Basic accessibility requirements
• Level AA: Industry-recommended compliance standard
• Level AAA: Advanced accessibility support

These criteria are technology-agnostic and apply to websites, web apps, and mobile platforms.

WCAG Principles

All WCAG 2.1 success criteria are grouped under four foundational principles, often abbreviated as POUR:

1. Perceivable: Present content in formats users can perceive, including text alternatives for images, video captions, and strong visual contrast for readability.
2. Operable: Design all interface elements to work with keyboards, screen readers, and other input methods, ensuring that navigation and interactions are accessible to everyone.
3. Understandable: Use clear language, consistent layouts, and descriptive error messages so users can easily understand and interact with content.
4. Robust: Ensure content is built with clean, semantic code that works reliably with current and future assistive technologies and browsers.

Together, these principles form the framework for evaluating each success criterion. If content fails to meet even one of these principles, it is not fully accessible.

Who Needs To Follow WCAG 2.1 Guidelines?

The WCAG 2.1 guidelines are essential for anyone building, designing, or maintaining digital products. Compliance is critical for:

• Web Developers and Designers: To ensure user interfaces meet accessibility standards during the build phase.
• Enterprises and Government Organizations: Many industries are legally required to meet Level AA conformance under regulations like the Americans with Disabilities Act (ADA), Section 508 in the U.S., and EN 301 549 in the EU.
• Educational Institutions: Schools, colleges, and universities that provide digital learning platforms or public web content must ensure accessibility for all learners.
• E-commerce and SaaS Providers: Failure to meet accessibility guidelines can lead to lawsuits, reputational damage, and loss of business from users who cannot engage with digital products.

Adopting WCAG 2.1 ensures compliance and expands the potential user base by removing barriers for millions of people.

How WCAG 2.1 Differs From WCAG 2.0

WCAG 2.1 expands upon WCAG 2.0 by adding 17 success criteria that address accessibility gaps not previously covered. 

These additions focus on improving access for users with mobile devices, low vision, and cognitive or learning disabilities.

Key differences include:

• Enhanced support for touch inputs and screen orientation
• Improved visual presentation for low vision users
• Clearer labeling and error identification for cognitive clarity

WCAG 2.1 retains all WCAG 2.0 criteria, ensuring backward compatibility. 

Meeting WCAG 2.1 requirements also satisfies WCAG 2.0 compliance, making it a practical standard for modern digital accessibility.

Understanding WCAG 2.1 Success Criteria

WCAG 2.1 includes 78 success criteria designed to make digital content accessible to many users. 

These criteria are divided across three conformance levels—A, AA, and AAA—and are organized under the four POUR principles: Perceivable, Operable, Understandable, and Robust.

Each success criterion defines a specific, testable condition. For example:

• Images must include descriptive alt text
• Navigation must be possible using only a keyboard
• Error messages must be clear and help users correct input
• Content must be readable by assistive technologies like screen readers.

This structured approach helps teams create digital products that are accessible, inclusive, and legally compliant.

WCAG 2.1 Level A Success Criteria Explained With Examples

Level A sets the minimum accessibility requirements. These criteria ensure basic access for users with disabilities and are essential for eliminating critical barriers.

Common Level A criteria include:

• Non-text content: All meaningful images must have alt text (SC 1.1.1).
• Keyboard accessibility: Users must be able to navigate without a mouse (SC 2.1.1).
• Focus order: Content must follow a logical tab order for keyboard users (SC 2.4.3).
• Name, role, value: UI elements must expose their function to assistive tech (SC 4.1.2).

Note: "SC" stands for Success Criterion. Each number follows a specific structure: the first digit indicates the POUR principle (Perceivable, Operable, Understandable, Robust), the second refers to the guideline, and the third represents the criterion itself (e.g., SC 1.1.1 = Principle 1 - Guideline 1.1 - Criterion 1).

For example, a website with a login form must allow users to tab through fields and submit the form without relying on a mouse. Alt text must clearly describe any logo or icon that carries meaning.

WCAG 2.1 Level AA Success Criteria Explained With Examples

Level AA is the standard most organizations aim to meet. It improves usability for a broader audience and often aligns with legal requirements under accessibility laws.

Notable Level AA criteria include:

• Contrast ratio: Text must maintain a 4.5:1 contrast ratio against the background (SC 1.4.3).
• Resizable text: Content should be readable when zoomed up to 200 percent (SC 1.4.4).
• Visible focus: A clear indicator must show which element is currently focused (SC 2.4.7).
• Labels in name: Visible labels must match accessible names (SC 2.5.3).

For instance, if a button says “Search,” the screen reader must also announce it as “Search,” not “Magnifying Glass.” Ensuring this consistency benefits both screen reader users and speech input users.

WCAG 2.1 Level AAA Success Criteria Explained With Examples

Level AAA represents the highest accessibility standard and is designed for advanced user support. While not legally required in most cases, it is valuable for specific use cases, such as educational platforms, government sites, or inclusive design leaders.

Examples of Level AAA criteria include:

• Sign language interpretation: Videos must provide sign language translations (SC 1.2.6).
• Extended audio descriptions: Additional narration must describe essential visual details (SC 1.2.8).
• Reading level: Content must be written at a lower secondary education level or provide supplemental help (SC 3.1.5).
• Context-sensitive help: Immediate help must be available for user inputs (SC 3.3.6).

For example, an online tutorial that includes video lessons must offer sign language and detailed descriptions to achieve Level AAA compliance.

How To Meet WCAG 2.1 Success Criteria

Successfully meeting WCAG 2.1 success criteria requires thoughtful design decisions and reliable testing throughout the development lifecycle. 

Following structured practices and using the right tools helps ensure digital experiences are accessible.

Here are essential steps to stay compliant:

• Use semantic HTML and ARIA roles so assistive technologies can interpret content accurately.
• Add alt text to non-text elements and ensure headings follow a logical hierarchy.
• Maintain minimum contrast ratios to meet Level AA or AAA visual standards.
• Enable full keyboard navigation, including proper tab order and visible focus indicators.
• Align visible labels with programmatic names to support screen readers and voice commands.
• Test accessibility across real devices and screen readers, not just simulated environments.

To simplify this process, teams can use BrowserStack’s free accessibility testing to run unlimited automated scans for WCAG 2.1 compliance. 

It detects common issues like missing alt text, low contrast, ARIA violations, and keyboard navigation errors across up to five unique user workflows per scan.

By combining best practices with continuous testing, teams can proactively address accessibility issues and build experiences that work for everyone.

WCAG 2.1 Implementation Best Practices [With Examples]

Implementing WCAG 2.1 successfully involves applying accessibility principles throughout the design and development process. The goal is to create interfaces that are not only compliant but usable for all individuals, including those with disabilities.

Best practices include:

• Integrate accessibility by including WCAG requirements in design systems and component libraries. For example, define heading hierarchies and focus styles in your foundational UI components.
• Use scalable layouts and responsive text that adapt across screen sizes and zoom levels. For example, use relative units like em or % for font sizes and spacing.
• Write clear, descriptive labels for links and buttons to ensure meaning is preserved across all contexts. For example, instead of "Click here," use "Download accessibility checklist."
• Structure forms correctly with associated labels, grouped fields, and meaningful error feedback. For example, use aria-describedby for inline error messaging linked to specific inputs.
• Test using real assistive technologies like screen readers and keyboard navigation. For example, use VoiceOver on Mac or NVDA on Windows to validate reading order and focus behavior.

These implementation strategies help teams embed accessibility into their workflow and minimize rework after development.

WCAG 2.1 Checklist for Developers and Designers

Use this checklist to guide accessibility reviews across design, development, and QA phases:

Design Phase

• Use accessible color palettes with proper contrast (minimum 4.5:1 for body text)
• Plan keyboard-friendly UI elements and navigation flow
• Ensure visible focus styles for all interactive elements
• Write meaningful labels and instructions for all form fields

Development Phase

• Use semantic HTML elements for structure and roles
• Add alt attributes to all meaningful visual elements
• Maintain proper heading order and DOM structure
• Apply appropriate ARIA roles where necessary
  

Testing Phase

• Navigate the entire site using only a keyboard
• Test with screen readers across major platforms
• Check tab order and focus management
• Run automated WCAG 2.1 scans using a testing platform

Following this checklist across all teams ensures consistent application of accessibility standards.

Legal Requirements and Compliance Risks Under WCAG 2.1

For many organizations, adhering to WCAG 2.1 is not just a best practice but a legal requirement. Several global regulations are based on WCAG success criteria and apply to public and private sector digital platforms.

Regulations based on WCAG:

• ADA (United States): Public-facing websites must meet accessible standards. Courts often refer to WCAG 2.1 Level AA.
• Section 508 (US Federal): Requires government and contractor sites to conform to WCAG.
• EN 301 549 (European Union): Applies to all public sector digital services in the EU.
• AODA (Ontario, Canada): Mandates compliance for businesses and nonprofit organizations.

Non-compliance risks:

• Legal complaints, demand letters, or lawsuits
• Settlements and financial penalties
• Public scrutiny and reputational damage
• Loss of potential users due to inaccessible services

By aligning digital experiences with WCAG 2.1, organizations reduce legal risk and enhance usability for all.

Conclusion

The WCAG 2.1 success criteria offer clear, testable guidelines that help teams deliver experiences usable by people of all abilities.

Every stage of the development process plays a role, from understanding its conformance levels to implementing best practices and performing regular audits. 

Using modern testing tools like BrowserStack Accessibility Testing, teams can run free automated scans to uncover compliance issues early and validate across real devices and screen readers.

Ultimately, meeting WCAG 2.1 standards means delivering compliant websites and more ethical, usable, and future-ready digital experiences.