aria-hidden

aria-hidden="true" is the exact inverse of visually hidden. One takes an element out of the picture and leaves it in the accessibility tree; this one leaves the pixels exactly where they are and deletes the node. That is the right tool for anything on screen that carries no information: the glyph inside an icon button whose label is already written in text, an ornament between a headline and a byline, a duplicated copy of a quotation, a decorative overlay of grain or scanlines. The reader loses nothing, because there was nothing there to lose.

It takes the whole subtree with it, and that is what separates it from the two attributes it gets confused with. Presentation role strips one element of its own semantics and leaves every child in place, so a table used for layout stops announcing rows while its cells keep being read. A decorative image with an empty alt drops one image. aria-hidden cuts a branch: the element, its children, and their children, with no way to mark a descendant present again from inside. Point it at a container and everything in that container is gone.

The first trap is the reason the attribute has a warning printed next to it in every reference. Hiding the node does nothing to focusability, so aria-hidden on anything focusable, or on any ancestor of anything focusable, produces a control a keyboard reaches and screen reader software insists does not exist. That combination has its own name and its own automated rule: see hidden but focusable. If the thing should not be reachable, it should not be reachable, and hiding it from software is not how you say so.

The second trap is the same mistake at page scale. aria-hidden is not inert. It hides from the tree and touches neither the focus order nor hit testing, so a background marked this way behind a dialog still takes clicks and still takes Tab stops. Sealing a region needs inert, or a <dialog> opened with showModal(), which makes everything outside the top layer inert for you. Reach for aria-hidden when something is genuinely decoration, and for inert when something is genuinely out of service.