Alternate text (alternative text) describes the appearance or function of an image on a page. Alternate text is read by screen readers used by visually impaired users, displayed in place of images when they fail to load, and indexed by search engine bots to better understand the content of the page. Alt text used in HTML code or in the corresponding field of a CMS (Content Management System), also known as an "alt attribute", "alt description", or technically incorrect as an "alt tag".