ARIA attributes must conform to valid values
ARIA attributes starting with
aria- must contain valid values. These values must be spelled correctly and correspond to values that make sense for a particular attribute in order to perform the intended accessibility function.
Why it Matters
ARIA attributes (i.e. starting with
aria-) must contain valid values. These values must be spelled correctly and correspond to values that make sense for a particular attribute to perform the intended accessibility function.
Many ARIA attributes accept a specific set of values. Allowed values, acceptable “undefined” values, and acceptable “default” values are required. Failure to comply with allowed values results in content that is not accessible to assistive technology users.
How to Fix the Problem
Ensure the value inside each attribute is spelled correctly and corresponds to a valid value.
aria-hidden="true" would pass, but
aria-hidden="rtue" would fail, as would
As another example, the
checkbox role only has three possible values:
mixed. Using any value other than one of those three will prevent the checkbox from being functional.
Particular caution must be used when specifying values for ARIA attributes, as factors such as the distinction between states and properties, role inheritance, undefined and default values can be confusing.
It is useful to take into consideration the following allowed state or property value types:
- Value representing either true or false, with a default “false” value.
- Value representing true or false, with an intermediate “mixed” value. Default value is “false” unless otherwise specified.
- Value representing true or false, with a default “undefined” value indicating the state or property is not relevant.
- ID reference
- Reference to the ID of another element in the same document
- ID reference list
- A list of one or more ID references.
- A numerical value without a fractional component.
- Any real numerical value.
- Unconstrained value type.
- One of a limited set of allowed values.
- token list
- A list of one or more tokens.
Undefined Value: The “undefined” value, when allowed on a state or property, is an explicit indication that the state or property is not set. The value is used on states and properties that support tokens, and the “undefined” value is a string that is one of the allowed tokens. It is also used on some states and properties that accept true/false values, when “undefined” has a different meaning than “false”.
These are generic types for states and properties, but do not define specific representation. See State and Property Attribute Processing for details on how these values are expressed and handled in host languages.
Default Value and Implicit Value for Role: Many states and properties have default values. Occasionally, the default value when used on a given role should be different from the usual default. Roles that require a state or property to have a non-standard default value indicate this in the “Implicit Value for Role”. This is expressed in the form “state or property name is new default value”. Roles that define this have the new default value for the state or property if the author does not provide an explicit value.
State and Property Values Reference: For complete information about allowed values, refer to the table of characteristics for each individual attribute at W3C WAI-ARIA 1.1 Supported States and Properties.
The Algorithm (in simple terms)
Checks all elements that contain WAI-ARIA attributes to ensure that the values of the attributes are valid.