ARIA property
aria-posinset
Which position this item holds in its set, when the markup does not contain the whole set.
It says where this item sits in the real set rather than in the fragment on screen. Together with aria-setsize it is what turns an endless list into item 5 of 200.
Which roles may carry aria-posinset
- Value
- integer
- Filed as
- A property, which is how ARIA files it and not a rule about how often it changes.
- Roles that inherit it
menuitemcheckbox,menuitemradio,treeitem
Those lists are not advice. Browsers are required to ignore a non-global attribute sitting on a role that does not support it, so aria-posinset on the wrong element is not weak, it is absent. You can read it in the DOM and nobody using a screen reader can.
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-posinset section of the ARIA specification.
Keeping aria-posinset true
Both halves have to be right, and they go stale in different ways. Positions break when the list is sorted, filtered or paged and the numbers stay attached to the old order. Nothing looks wrong, because the numbers are still numbers. Compute them from the data on every render rather than assigning them once at build time. And keep the pair together, because a position with no total behind it leaves the listener holding half a fact.
How aria-posinset 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-posinset
- aria-checked Whether a checkbox, radio or switch is on, off, or partly on.
- aria-colindex Which column a cell is in, counting from the real table rather than what is shown.
- aria-disabled Says a control is present but not available. Unlike the disabled attribute, it stays focusable, so people can still find out it is there.
- aria-expanded Whether the thing this control opens is currently open.
- aria-haspopup Says this control opens something, and what kind of thing it opens. A menu, a dialog, a listbox.
- aria-level The depth of a heading or a tree item, counting from one.
- aria-rowindex Which row this is, counting from the real table.
- aria-selected Whether an option, tab or row is the chosen one.
Every ARIA state and property · Every ARIA role · ARIA explained