Alt text (alternative text) is a description added to an image's HTML tag to provide context for users who cannot see the image. It is displayed in place of an image if the image fails to load and is also read by screen readers to assist visually impaired users.
Alt-text is important for both accessibility and SEO. It allows search engines to understand what the image is about, which can improve the page's search ranking. For example, the alt-text for an image of a dog could be "golden retriever playing in the park," helping search engines index the image properly. Well-written alt-text enhances user experience and website visibility.