Alt Text for Images

Alt text is a text alternative that communicates an image’s information or function. A screen reader can present this text as speech or Braille. The right wording depends on why the image appears on the page. Pick one image and identify what it contributes.

Start by deciding whether an image conveys important information, performs a function, or serves only as decoration. For informative images, provide a short description conveying the essential information. Context determines which details matter: WAI explains that a bird’s exact appearance may matter more on a website about birds than on one about parks. Images Tutorial

For functional images used as links or buttons, describe the destination or action. In a hypothetical example, a document icon is the only content of a link to an employee handbook in PDF, a document file format. “Employee handbook (PDF)” identifies the destination more clearly than “PDF document icon,” which describes its appearance.

For an image whose only purpose is visual decoration, provide an empty text alternative. In page code, the alt attribute supplies an image’s alternative text; alt="" gives it an empty value. In a hypothetical travel blog, a sunset photo used only as decoration would receive this empty value. A caption alone does not establish that an image is decorative: first determine whether the image contributes information important to understanding the page.

A short description is not sufficient for every image. For complex images such as graphs and diagrams, provide a complete text equivalent of the data or detailed information. WAI also advises avoiding readable text within images unless the image is a logo; when images of text are used, their text alternatives should contain the same words. These decisions depend on the author understanding the image’s usage, context, and content. The tutorial provides implementation guidance, not experimental proof or a guarantee of legal compliance. Images Tutorial

• Official guidance: WAI distinguishes informative, decorative, and functional images. Their text alternatives respectively convey essential information, use an empty value for decoration alone, or describe the link or button’s function [1]
• Official guidance: Complex images need a complete text equivalent of their data or detailed information. The tutorial does not impose a universal one-sentence limit on text alternatives [1]
• Scope of guidance: The tutorial combines resources concerning Non-text Content at Level A, Images of Text at Level AA, and Images of Text (No Exception) at Level AAA. These are different WCAG conformance levels; the overview does not reproduce each criterion’s full conditions and exceptions [1]

The supplied source is official implementation guidance, not an experiment measuring navigation, comprehension, or behavioral effects. It does not establish universal benefits or guarantee legal compliance. Its category summaries should not be treated as the complete requirements of WCAG, the Web Content Accessibility Guidelines.

The old “Henry et al. (2014)” citation and its claimed navigation finding are unverified by the supplied evidence and have been removed. WAI’s Images Tutorial replaces that attribution as the guidance source. The earlier 2024 date assigned to the tutorial is also removed; the supplied bibliography records its year as unknown. The handbook and sunset examples are hypothetical applications of the guidance.