The correct setting is overflow: auto;. The CSS overflow property controls how content behaves when it does not fit inside an element's padding box. The requirement has three parts: keep the text inside the element's border, avoid unnecessary scrollbars, and avoid losing text. overflow: hidden clips overflowing content and does not provide a user-visible scrollbar, so text can become inaccessible. overflow: visible allows excess content to render outside the element's box, failing the containment requirement. overflow: scroll makes the element scrollable, but user agents display scrollbars whether or not content is actually overflowing, which violates the requirement to avoid unneeded scrollbars. MDN describes overflow: auto as clipping overflow content at the padding box while allowing it to be scrolled into view, with scrollbars displayed only when content is actually overflowing. This makes auto the precise choice for a controlled text container. References
/topics: CSS overflow, scroll containers, content clipping, layout flow, preserving overflowing content.