Z-Order

Z-order refers to the front-to-back layering sequence of overlapping objects on a 2-D digital canvas, determining which objects appear in front of or behind others. In accessibility, Z-order is significant because screen readers in presentation software often read objects according to their Z-order (creation order) rather than their visual reading order, meaning a title placed at the top of a slide may be read last if it was the last object created. This disconnect between visual layout and screen reader navigation order is a major barrier for blind users trying to understand slides, and is why accessible document authoring guidelines emphasize setting an explicit reading order separate from Z-order.