Success Criteria Structure — How WCAG Criteria Are Organized

In this tutorial, you will learn about Success Criteria Structure. We cover key concepts, practical examples, and best practices to help you master this topic.

WCAG success criteria are structured with a unique identifier, conformance level, description, sufficient techniques, advisory techniques, and failures, organized under guidelines that belong to one of the four POUR principles.

What You'll Learn

You will learn how WCAG success criteria are organized, numbered, and documented, including how to read understanding documents and find the right techniques for each criterion.

Why It Matters

Understanding the structure helps you navigate WCAG documentation efficiently, find relevant techniques, and accurately assess conformance.

Real-World Use

DodaTech's Accessibility specialists use the WCAG Understanding documents as their primary reference. Each criterion's page includes links to sufficient techniques that provide tested, reliable implementations.

flowchart TD
  A[WCAG Structure] --> B[Principle]
  B --> C[Guideline]
  C --> D[Success Criterion]
  D --> E[Sufficient Techniques]
  D --> F[Advisory Techniques]
  D --> G[Failures]
  E --> H[How to meet it]
  G --> I[What fails it]

Anatomy of a Success Criterion

Each success criterion has:

• A unique number: principle.guideline.criterion (e.g., 1.4.3)
• A title: Contrast (Minimum)
• A conformance level: A, AA, or AAA
• A description of the requirement
• A link to the Understanding document
• Links to sufficient techniques, advisory techniques, and failures

How to Read a Criterion Number

The first digit is the principle (1=Perceivable, 2=Operable, 3=Understandable, 4=Robust). The second digit is the guideline number. The third digit is the criterion number.

Example: 2.4.7 — Principle 2 (Operable), Guideline 4 (Navigable), Criterion 7 (Focus Visible).

Understanding Documents

Each success criterion has an Understanding document at w3.org that explains the intent, benefits, examples, and resources. These documents are the authoritative reference.

function getCriterionInfo(criterionNumber) {
  const [principle, guideline, criterion] = criterionNumber.split('.').map(Number);
  const principles = { 1: 'Perceivable', 2: 'Operable', 3: 'Understandable', 4: 'Robust' };
  const levels = { A: 'Minimum', AA: 'Legal standard', AAA: 'Highest' };

  return {
    number: criterionNumber,
    principle: principles[principle],
    url: `https://www.w3.org/WAI/WCAG22/Understanding/${getUnderstandingSlug(criterionNumber)}.html`
  };
}

function getUnderstandingSlug(criterionNumber) {
  const slugs = {
    '1.1.1': 'non-text-content',
    '1.4.3': 'contrast-minimum',
    '2.1.1': 'keyboard',
    '2.4.7': 'focus-visible',
    '4.1.2': 'name-role-value'
  };
  return slugs[criterionNumber] || criterionNumber.replace(/\./g, '-');
}

console.log(getCriterionInfo('1.4.3'));

Expected output:

{
  number: '1.4.3',
  principle: 'Perceivable',
  url: 'https://www.w3.org/WAI/WCAG22/Understanding/contrast-minimum.html'
}

Techniques

Sufficient Techniques

Tested, approved ways to meet a criterion. Following a sufficient technique guarantees you meet that criterion.

Advisory Techniques

Recommended practices that improve accessibility but are not strictly required. Implementing advisory techniques is good practice.

Failures

Known patterns that fail a criterion. Avoid these patterns. Automated tools can detect many failures.

Common Mistakes

1. Reading Only the Success Criterion Text

The criterion text is brief. The Understanding document provides context, intent, and examples.

2. Not Looking at Sufficient Techniques

Sufficient techniques provide tested implementations. Reinventing solutions wastes time and may miss requirements.

3. Confusing Advisory with Sufficient

Advisory techniques are optional. Sufficient techniques are required for conformance. Know the difference.

4. Ignoring Failures

Failure examples help you identify common mistakes. Review failures to ensure you do not unintentionally violate criteria.

5. Not Bookmarking Understanding Documents

The Understanding documents are the authoritative reference. Bookmark them for quick access.

6. Using Outdated Techniques

WCAG 2.2 may have updated techniques. Ensure you are using techniques for the version you target.

7. Not Checking for New Techniques

New techniques are added over time. Periodically review the Techniques section for updates.

Practice Questions

1. What does the criterion number 2.4.11 tell you?

Principle 2 (Operable), Guideline 4 (Navigable), Criterion 11 (Focus Appearance).

2. What is the difference between sufficient and advisory techniques?

Sufficient techniques guarantee conformance. Advisory techniques are recommended but not sufficient alone.

3. Where is the authoritative documentation for each success criterion?

The Understanding document at w3.org/WAI/WCAG22/Understanding/.

4. What is a failure in WCAG terminology?

A known pattern that fails a success criterion. Avoid these patterns in your implementation.

5. Challenge: Pick one WCAG success criterion. Read its Understanding document. Identify one sufficient technique and one failure pattern.

FAQ

Mini Project

Create a reference table of the 10 most commonly cited WCAG success criteria. For each, list the number, title, level, one sufficient technique, and one failure to avoid.

What's Next

Learn about Sufficient Techniques for meeting WCAG criteria with tested, reliable implementations. Then explore Advisory Techniques for improving accessibility beyond minimum requirements.