• June 1, 2025

ARIA Attribute Value Validity

Rule ID: aria-valid-attr-value
Ruleset: axe-core 4.10
User Impact: Critical
Guidelines: WCAG 2.1 (A), WCAG 2.0 (A), WCAG 2.2 (A), EN 301 549

How to Fix the Problem

Ensure that each ARIA attribute (attributes beginning with aria-) is assigned a value that is valid according to the WAI-ARIA specification.

Examples:

• ✅ Correct: <div aria-hidden="true">

• ❌ Incorrect: <div aria-hidden="rtue">

• ❌ Incorrect: <div aria-hidden="pizza">

For roles such as checkbox, allowed values for aria-checked are only:

• true

• false

• mixed

Using any value outside these results in a failure of functionality and accessibility.

Guidelines to Follow:

• Spelling matters. Values must be exactly as specified (e.g., “true”, not “TRUE” or “tru”).

• Use appropriate value types. Each ARIA attribute supports one or more of the following value types:

  • true/false (e.g., aria-hidden="false")

  • tristate (e.g., aria-checked="mixed")

  • true/false/undefined

  • ID reference (e.g., aria-labelledby="section1")

  • ID reference list

  • integer

  • number

  • string

  • token

  • token list

Check the official WAI-ARIA 1.1 specification for a full list of valid attributes and their expected values.

Additional Considerations:

• Undefined values: Some states or properties allow "undefined" as a valid option to indicate that the property is not set.

• Default vs. Implicit values: Certain roles change the default values of ARIA properties. Be aware of role-based expectations.

Why it Matters

ARIA attributes enable assistive technologies (AT), like screen readers, to interpret and interact with dynamic content. If these attributes contain invalid values:

• AT cannot properly interpret them.

• Users relying on assistive technologies may not receive accurate or actionable information.

• The interactive components may become non-functional or misleading.

Correct ARIA usage ensures a seamless, inclusive, and accessible user experience.

Rule Description

ARIA attributes must include only valid, semantically correct values. Each attribute has a defined set of acceptable values, and deviations—even small spelling mistakes—can render the attribute non-functional or cause unexpected behavior in assistive technologies.

The Algorithm (in Simple Terms)

1. Identify elements with attributes that start with aria-.

2. For each attribute, check:

   • Is the value among the allowed options?

   • Is it spelled exactly as specified in the standard?

3. Flag the element if any attribute has an invalid or unsupported value.