The badge on a Twitter image that includes a description is labeled ALT.
ALT abbreviates “alternative text,” the technical term for a text description attached to an image. Selecting the badge reveals the description, making visual information available to people who use screen readers or have difficulty seeing the picture.
Twitter introduced image-description support in its mobile apps in 2016. In 2022, it rolled out a more visible ALT badge globally, so anyone viewing a post could tell that descriptive text had been supplied. Descriptions can explain the subject, setting, action, or important text shown in an image.
ALT is not the same as a GIF label. A GIF label identifies moving media, while the ALT badge indicates that an image or GIF has an accompanying description. The badge therefore signals accessibility information, not image format, file type, or account status.