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Published: September 11, 2026
This study reviews evidence for choosing and testing text alternatives according to image purpose. Sources were observed September 11, 2026.
Methodology
We used a structured documentary review of WCAG 2.2, WAI image tutorials, HTML, accessibility mappings, and government guidance. Concepts were coded by image function and converted into reviewable production decisions. No automated alt-text generator was evaluated.
Scope, population, and observation window
The population is visitors encountering informative, functional, decorative, complex, or text-bearing images, including people using screen readers or browsing without loaded images. Scope covers HTML images and linked images on content pages. Video description, canvas, and social-platform previews are excluded. The review reflects guidance accessible on September 11, 2026.
Evidence synthesis
The evidence makes context central. Informative images need concise equivalents, functional images need the action or destination, decorative images generally need an empty alternative, and complex graphics need a nearby fuller explanation. A filename or generic object label rarely captures purpose.
Inference and causal boundaries
Inference: teams should approve image purpose before drafting text, then inspect final HTML and the page with images unavailable. Meeting a text-alternative requirement does not establish that prose is accurate, concise, or useful. Evidence here cannot support causal claims about engagement, conversion, or search ranking.
Limitations
This review did not test comprehension, multilingual wording, AI-generated descriptions, SVG accessibility, or a specific screen-reader and browser matrix. Judgment remains necessary because identical assets can serve different purposes on different pages.
Sources
- WCAG 2.2
- W3C Understanding Non-text Content
- WAI Images Tutorial
- WAI Informative Images
- WAI Decorative Images
- WAI Functional Images
- WAI Complex Images
- WHATWG Embedded Content
- HTML Accessibility API Mappings
- GOV.UK Images Guidance
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