Indicates what notifications the user agent will trigger when the accessibility tree within a live region is modified.
Description

Indicates what notifications the user agent will trigger when the accessibility tree within a live region is modified. See related aria-atomic.

The attribute is represented as a space delimited list of the following values: additions, removals, text; or a single catch-all value all.

This is used to describe semantically meaningful changes, as opposed to merely presentational ones. For example, nodes that are removed from the top of a log are merely removed for purposes of creating room for other entries, and the removal of them does not have meaning. However, in the case of a buddy list, removal of a buddy name indicates that they are no longer online, and this is a meaningful event. In that case aria-relevant will be set to all. When the aria-relevant attribute is not provided, the default value, additions text, indicates that text modifications and node additions are relevant, but that node removals are irrelevant.

Note: aria-relevant values of removals or all are to be used sparingly. Assistive technologies only need to be informed of content removal when its removal represents an important change, such as a buddy leaving a chat room.

Note: Text removals should only be considered relevant if one of the specified values is 'removals' or 'all'. For example, for a text change from 'foo' to 'bar' in a live region with a default aria-relevant value, the text addition ('bar') would be spoken, but the text removal ('foo') would not.

aria-relevant is an optional attribute of live regions. This is a suggestion to assistive technologies, but assistive technologies are not required to present changes of all the relevant types.

When aria-relevant is not defined, an element's value is inherited from the nearest ancestor with a defined value. Although the value is a token list, inherited values are not additive; the value provided on a descendant element completely overrides any inherited value from an ancestor element.

When text changes are denoted as relevant, user agents MUST monitor any descendant node change that affects the text alternative computation of the live region as if the accessible name were determined from contents (nameFrom: contents). For example, a text change would be triggered if the HTML alt attribute of a contained image changed. However, no change would be triggered if there was a text change to a node outside the live region, even if that node was referenced (via aria-labelledby) by an element contained in the live region.

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ARIA