alt text; fallback text; image description text
Computing term for text that replaces or describes an image when it cannot be displayed, commonly used in web accessibility and HTML.
If the image cannot be displayed, alt text will be shown instead.
For web accessibility, please set appropriate alt text for all images.
Compound of 代替 (だいたい, 'substitute') and テキスト ('text'), likely a direct translation of the English computing term 'alt text'.