Longdesc

An HTML attribute historically used to provide extended descriptions for images that require more detail than can fit in an alt attribute. The longdesc attribute contained a URL pointing to a separate page or anchor with the full description. While part of HTML 4.01 and initially included in HTML5, longdesc was later moved to an extension specification due to poor browser support and low adoption. Modern alternatives include using aria-describedby to reference description text within the same page, or providing description links adjacent to images.