Alt Text

Alt text, the alt attribute on HTML image elements, is the textual alternative that conveys an image's information to users who cannot see it — primarily screen-reader users who hear the alt text spoken in place of the image, but also users with images disabled, slow connections, or broken images displayed. Alt text is the single most fundamental and most-violated accessibility requirement on the web, codified in WCAG 1.1.1 Non-text Content (Level A — the most basic conformance level) and required by virtually every accessibility law. Writing good alt text requires understanding the image's purpose, which falls into roughly four categories: informative images that convey content not in surrounding text (alt text should describe the information — "Bar chart showing Q3 revenue of $4.2M, up 18% year over year"), functional images like icon buttons or linked logos (alt text should describe the function — "Search" for a magnifying-glass button, not "Magnifying glass icon"), decorative images that add visual appeal but no information (alt="" with the explicit empty string, so screen readers skip them — never alt="decorative" or alt="image"), and complex images like charts, diagrams, and infographics (short alt text plus a longer text description elsewhere on the page, often referenced with aria-describedby). The cardinal sins: missing alt attributes entirely (screen readers may read the filename — "IMG_4502.JPG" is not a useful alt text), alt text that says "image of" or "picture of" (redundant — screen readers already announce that), alt text that just repeats adjacent visible text (the screen-reader user hears it twice), and alt text on decorative images that should have been empty. Modern AI-generated alt text from multimodal LLMs (GPT-4V, Claude 3.5 Sonnet, Gemini) can produce decent first-draft descriptions but typically require human review for correctness, context, and avoiding hallucination. Tooling: axe-core flags missing alt; the WAVE browser extension visualizes alt text on every image; the Photosensitivity Analysis Tool and color-blindness simulators address other related image-accessibility concerns. PDF and Office documents have their own alt-text requirements (described under PDF/UA) with parallel mechanics. For Digital Experience Platforms, alt text is the most fundamental boundary between "the image carries information" and "your blind users see nothing."

Alt-text discipline under a Magic Quadrant DXP: Centralpoint enforces alt-text completeness across client content for 25 years — the foundational accessibility discipline that underpins the Gartner Magic Quadrant DXP positioning where every user must receive the experience. Alt-text auditing runs on-premise, lineage is audit-graded, and inclusive experiences deploy through one line of JavaScript.


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