WCAG 2.1 Section 5.1: Interpreting Normative Requirements

Estimated read time: 4–5 minutes

What Does "Normative" Mean in WCAG?

In WCAG 2.1, the main content is normative—meaning it defines requirements that impact whether a website or digital product is considered accessible and conformant. Normative sections set the rules you must follow to claim conformance with WCAG.

Normative: Required for conformance. These are the rules you must meet.
Informative: For information only. These help you understand the guidelines but are not required for conformance.

Sections marked as "non-normative," introductory material, appendices, diagrams, examples, and notes are informative. They provide helpful advice and context, but do not create requirements.

Key Terms: MUST, SHOULD, MAY, etc.

WCAG uses specific keywords to indicate the strength of requirements, as defined in RFC 2119 :

MUST: This is an absolute requirement. You must do this to conform.
MUST NOT: This is absolutely prohibited.
SHOULD: This is recommended, but not strictly required.
SHOULD NOT: This is not recommended, but not strictly prohibited.
MAY: This is optional. You can choose to do this or not.
RECOMMENDED / NOT RECOMMENDED: Indicates best practices, but not strict requirements.

These keywords are used throughout WCAG to clarify what is required, what is recommended, and what is optional.

How to Interpret Normative Requirements in WCAG

Only the normative sections of WCAG 2.1 define what is required for accessibility conformance.
Informative content (such as examples, notes, and appendices) is there to help you understand and apply the guidelines, but does not affect conformance.
When you see the keywords above, interpret them as described. For example, if a success criterion says you MUST provide alt text for images, this is a strict requirement.

Example

If a guideline says, "All images MUST have alternative text," then providing alt text is required for conformance. If it says, "It is RECOMMENDED to use descriptive alt text," then it is best practice, but not required.

Why Does This Matter?

Understanding the difference between normative and informative content—and the meaning of key terms—ensures you:

Know exactly what is required for accessibility conformance
Can distinguish between rules and helpful advice
Avoid common mistakes when making or evaluating conformance claims

References & Further Reading

Understanding normative requirements is essential for anyone working with web accessibility standards. By following the normative rules and using informative content for guidance, you can ensure your digital content is truly accessible and compliant.

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