ARIA property
aria-atomic
Whether an update should be read whole, or only the part that changed.
Set it to true and a change anywhere inside the region makes the whole region get read out. Leave it alone and only the changed part is announced, which is why a counter going from 59 to 60 can announce as a bare 60 with nothing around it.
Which roles may carry aria-atomic
- Value
- true/false
- Filed as
- A property, which is how ARIA files it and not a rule about how often it changes.
- Roles that may carry it
- Any role. This one is global, which is why no individual role lists it.
Global means no role has to grant permission for it. There is one more place to check, because ARIA in HTML sets rules per element as well as per role, and it allows no aria-* attributes at all on a datalist or on the html element. Past that, the way a global attribute goes wrong is rarely where it sits. It is whether it is still true, which is the next section.
Every role above comes from the specification's own list for this attribute, checked name for name. The normative definition stays with the W3C, in the aria-atomic section of the ARIA specification.
Keeping aria-atomic true
The default is false, and browsers work out which value applies by starting at the changed element and walking up to the first ancestor that sets one. So a value set high in the page reaches everything below it, and a value on a child overrides what it inherited. That makes this an attribute to place deliberately rather than sprinkle. One thing to know if you are using the roles instead. A status region carries an implicit true and a plain polite live region does not, so the two announce at the same urgency and read out different amounts. Some environments do not honour the implicit one either, so writing it out on a status region is the safer call.
How aria-atomic gets checked
There are test rules that check an ARIA attribute is one that exists, is allowed on the role underneath it, and carries a value of the right type. What they map to is ARIA's own author requirements rather than any WCAG criterion, so a misplaced attribute breaks ARIA without being a WCAG failure by itself. It becomes one under 4.1.2 Name, Role, Value the moment the missing or wrong value means the control's state cannot be worked out programmatically, which is what usually happens next.
Nothing automated catches the failure this page is about. A stale value is a valid value, on a permitted role, with the right type. It is only wrong about the world.
Attributes you will meet alongside aria-atomic
- aria-busy Says a region is still being updated, so wait before announcing it.
- aria-controls Points at what this control operates. A combobox has to say what it opens.
- aria-current Marks the one item in a set that represents the here and now, such as the current page in a nav.
- aria-describedby Points at further description, read after the name. Hints and error text usually go here.
- aria-details Points at richer explanation elsewhere in the page, which people can navigate to rather than have read out.
- aria-flowto Overrides reading order by pointing at what should be read next. Rarely the right answer.
- aria-hidden Removes an element from the accessibility tree while leaving it on screen.
- aria-keyshortcuts Lists the keyboard shortcuts that activate this control, so they can be announced and checked for clashes.
Every ARIA state and property · Every ARIA role · ARIA explained