The HTML aria-setsize attribute
The aria-setsize attribute states the total number of items in a set — a list, listbox, menu or tree — when the DOM contains only some of them. Pair it with aria-posinset so screen readers can say "item 5 of 200".
Overview
The aria-setsize attribute defines the total number of items in a set when not all are in the DOM.
It describes an element's place in a larger set or hierarchy. This matters when not all items are present in the DOM at once — a virtualized list or a lazy-loaded tree — so assistive technology cannot count them itself. For fully-rendered native lists, the browser computes position and size for you.
Like all ARIA, aria-setsize changes only the accessibility tree — what assistive technology perceives — never the element's behavior or appearance. The first rule of ARIA applies: if a native HTML element or attribute conveys this, use that instead, and only reach for ARIA when nothing native fits.
Syntax
<li role="option" aria-setsize="200" aria-posinset="5"> … </li>Values
| Value |
|---|
| An integer (use -1 if the total is unknown). |
Example
<li role="option" aria-setsize="200" aria-posinset="5">Item</li>Best practices
- Follow the first rule of ARIA — use a native HTML element or attribute that conveys this where one exists, rather than adding ARIA.
- Use these when the full set is not in the DOM (virtualized lists, lazy-loaded trees).
- Set aria-posinset and aria-setsize together for each item.
- For fully-rendered native lists, let the browser compute position and size instead.