How many ARIA attributes are there?

WAI-ARIA 1.2 defines 48: 10 states and 38 properties. Two of them, aria-grabbed and aria-dropeffect, are deprecated. The ARIA 1.3 working draft adds a few more, such as aria-description.

What is the difference between aria-label and aria-labelledby?

aria-label holds the name as a string. aria-labelledby points at the id of one or more elements whose text becomes the name, and takes precedence when both are present. Both replace the name the element would otherwise get from its content.

Does a misspelled ARIA attribute cause an error?

No. Browsers ignore unknown attributes silently, so a misspelling such as aria-labeledby simply has no effect. That is why a check that compares attribute names with the specification is useful.

Reference

WAI-ARIA states and properties

WAI-ARIA 1.2 defines 48 aria-* attributes: 10 states, such as aria-expanded, aria-checked and aria-hidden, which change with interaction, and 38 properties, such as aria-label, aria-labelledby, aria-describedby and aria-live, which describe an element more permanently. Two of them, aria-grabbed and aria-dropeffect, have been deprecated since ARIA 1.1. An attribute outside this list is not ARIA: assistive technology ignores it, and whatever it was meant to convey never reaches the user.

The states and properties defined by WAI-ARIA 1.2 (W3C Recommendation), with their definition and what the VeriFixScan ARIA checks do with each.
Attribute	Kind	Definition	Status in ARIA 1.2	In a scan
aria-activedescendant	Property	Identifies the currently active element when DOM focus is on a composite widget, combobox, textbox, group, or application.	Current	Name recognised.
aria-atomic	Property	Indicates whether assistive technologies will present all, or only parts of, the changed region based on the change notifications defined by the aria-relevant attribute.	Current	Name recognised.
aria-autocomplete	Property	Indicates whether inputting text could trigger display of one or more predictions of the user's intended value for a combobox, searchbox, or textbox and specifies how predictions would be presented if they were made.	Current	Name recognised.
aria-busy	State	Indicates an element is being modified and that assistive technologies MAY want to wait until the modifications are complete before exposing them to the user.	Current	Name recognised.
aria-checked	State	Indicates the current "checked" state of checkboxes, radio buttons, and other widgets.	Current	Name recognised.
aria-colcount	Property	Defines the total number of columns in a table, grid, or treegrid.	Current	Name recognised.
aria-colindex	Property	Defines an element's column index or position with respect to the total number of columns within a table, grid, or treegrid.	Current	Name recognised.
aria-colspan	Property	Defines the number of columns spanned by a cell or gridcell within a table, grid, or treegrid.	Current	Name recognised.
aria-controls	Property	Identifies the element (or elements) whose contents or presence are controlled by the current element.	Current	Name recognised. Referenced ids must exist (accessibility.aria_references).
aria-current	State	Indicates the element that represents the current item within a container or set of related elements.	Current	Name recognised.
aria-describedby	Property	Identifies the element (or elements) that describes the object.	Current	Name recognised. Referenced ids must exist (accessibility.aria_references).
aria-details	Property	Identifies the element that provides a detailed, extended description for the object.	Current	Name recognised.
aria-disabled	State	Indicates that the element is perceivable but disabled, so it is not editable or otherwise operable.	Current	Name recognised.
aria-dropeffect	Property	Indicates what functions can be performed when a dragged object is released on the drop target.	Deprecated in ARIA 1.1	Name recognised.
aria-errormessage	Property	Identifies the element that provides an error message for an object.	Current	Name recognised.
aria-expanded	State	Indicates whether a grouping element owned or controlled by this element is expanded or collapsed.	Current	Name recognised.
aria-flowto	Property	Identifies the next element (or elements) in an alternate reading order of content which, at the user's discretion, allows assistive technology to override the general default of reading in document source order.	Current	Name recognised.
aria-grabbed	State	Indicates an element's "grabbed" state in a drag-and-drop operation.	Deprecated in ARIA 1.1	Name recognised.
aria-haspopup	Property	Indicates the availability and type of interactive popup element, such as menu or dialog, that can be triggered by an element.	Current	Name recognised.
aria-hidden	State	Indicates whether the element is exposed to an accessibility API.	Current	Name recognised. true on a focusable element is flagged (accessibility.aria_hidden).
aria-invalid	State	Indicates the entered value does not conform to the format expected by the application.	Current	Name recognised.
aria-keyshortcuts	Property	Indicates keyboard shortcuts that an author has implemented to activate or give focus to an element.	Current	Name recognised.
aria-label	Property	Defines a string value that labels the current element.	Current	Name recognised. An empty value is flagged.
aria-labelledby	Property	Identifies the element (or elements) that labels the current element.	Current	Name recognised. Referenced ids must exist (accessibility.aria_references).
aria-level	Property	Defines the hierarchical level of an element within a structure.	Current	Name recognised.
aria-live	Property	Indicates that an element will be updated, and describes the types of updates the user agents, assistive technologies, and user can expect from the live region.	Current	Name recognised.
aria-modal	Property	Indicates whether an element is modal when displayed.	Current	Name recognised.
aria-multiline	Property	Indicates whether a text box accepts multiple lines of input or only a single line.	Current	Name recognised.
aria-multiselectable	Property	Indicates that the user may select more than one item from the current selectable descendants.	Current	Name recognised.
aria-orientation	Property	Indicates whether the element's orientation is horizontal, vertical, or unknown/ambiguous.	Current	Name recognised.
aria-owns	Property	Identifies an element (or elements) in order to define a visual, functional, or contextual parent/child relationship between DOM elements where the DOM hierarchy cannot be used to represent the relationship.	Current	Name recognised.
aria-placeholder	Property	Defines a short hint (a word or short phrase) intended to aid the user with data entry when the control has no value. A hint could be a sample value or a brief description of the expected format.	Current	Name recognised.
aria-posinset	Property	Defines an element's number or position in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM.	Current	Name recognised.
aria-pressed	State	Indicates the current "pressed" state of toggle buttons.	Current	Name recognised.
aria-readonly	Property	Indicates that the element is not editable, but is otherwise operable.	Current	Name recognised.
aria-relevant	Property	Indicates what notifications the user agent will trigger when the accessibility tree within a live region is modified.	Current	Name recognised.
aria-required	Property	Indicates that user input is required on the element before a form may be submitted.	Current	Name recognised.
aria-roledescription	Property	Defines a human-readable, author-localized description for the role of an element.	Current	Name recognised.
aria-rowcount	Property	Defines the total number of rows in a table, grid, or treegrid.	Current	Name recognised.
aria-rowindex	Property	Defines an element's row index or position with respect to the total number of rows within a table, grid, or treegrid.	Current	Name recognised.
aria-rowspan	Property	Defines the number of rows spanned by a cell or gridcell within a table, grid, or treegrid.	Current	Name recognised.
aria-selected	State	Indicates the current "selected" state of various widgets.	Current	Name recognised.
aria-setsize	Property	Defines the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM.	Current	Name recognised.
aria-sort	Property	Indicates if items in a table or grid are sorted in ascending or descending order.	Current	Name recognised.
aria-valuemax	Property	Defines the maximum allowed value for a range widget.	Current	Name recognised.
aria-valuemin	Property	Defines the minimum allowed value for a range widget.	Current	Name recognised.
aria-valuenow	Property	Defines the current value for a range widget.	Current	Name recognised.
aria-valuetext	Property	Defines the human readable text alternative of aria-valuenow for a range widget.	Current	Name recognised.

States, properties, and why the difference matters

A state is expected to change while the page is used: a menu button's `aria-expanded` goes from false to true, a checkbox's `aria-checked` follows the click. The script that changes the visual state has to change the ARIA state with it, or assistive technology announces something stale.

A property describes the element more lastingly: its label, what it controls, what describes it, whether it is a live region. Properties are usually set once in the markup.

The distinction is descriptive — both are attributes, both are read the same way — but it points at the most common ARIA failure: a state written once in the HTML and never updated.

The first rule is to need fewer of them

The W3C guidance on using ARIA starts with one rule: when a native HTML element or attribute already has the semantics and behaviour needed, use it instead of adding ARIA to something else. A `<button>` needs no `role` and no `aria-pressed` to be a button.

ARIA changes what assistive technology is told, not how the element behaves. A `div` with `role="button"` is announced as a button and still does nothing with the keyboard until script makes it.

Several attributes only make sense on particular roles — `aria-checked` on checkboxes and similar widgets, `aria-valuenow` on range widgets, `aria-sort` on column headers. Using them elsewhere is valid spelling and meaningless.

What a scan validates

`accessibility.aria_validity` compares every `aria-*` attribute in the served HTML with a list of known attribute names, and every `role` value with a list of known roles. A name that is not on the list is reported, as is an empty `aria-label`.

That list holds the 48 attributes above and five more from the ARIA 1.3 working draft — `aria-braillelabel`, `aria-brailleroledescription`, `aria-colindextext`, `aria-rowindextext` and `aria-description` — so those five are accepted rather than reported as typos, although they are not part of the ARIA 1.2 Recommendation.

`accessibility.aria_references` checks that the ids named by `aria-labelledby`, `aria-describedby` and `aria-controls` exist in the same document, and `accessibility.aria_hidden` flags focusable elements marked `aria-hidden="true"`.

The checks read the HTML the server returned. They do not check that an attribute is allowed on the element's role, that its value is of the right type, or that a state is updated when the interface changes.

Frequently asked questions

How many ARIA attributes are there?: WAI-ARIA 1.2 defines 48: 10 states and 38 properties. Two of them, aria-grabbed and aria-dropeffect, are deprecated. The ARIA 1.3 working draft adds a few more, such as aria-description.
What is the difference between aria-label and aria-labelledby?: aria-label holds the name as a string. aria-labelledby points at the id of one or more elements whose text becomes the name, and takes precedence when both are present. Both replace the name the element would otherwise get from its content.
Does a misspelled ARIA attribute cause an error?: No. Browsers ignore unknown attributes silently, so a misspelling such as aria-labeledby simply has no effect. That is why a check that compares attribute names with the specification is useful.

Sources

VeriFixScan crawls a site and applies its checks to every page it reaches, keeping the evidence behind each finding. Scanning one website is free.

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