What is alt text, and why it matters for SEO and accessibility

Alt text — short for "alternative text" — is a short written description of an image. It does not appear visually on the page for most users, but it is read aloud by screen readers used by people who are blind or have low vision, and it is read by search engine crawlers that cannot "see" images.

The accessibility case

When an image carries information and has no alt text, a screen reader either skips it entirely or reads the file name — which is rarely useful. A decorative product photo named "IMG_4821.jpg" tells a blind visitor nothing. Good alt text ("A tan leather hiking boot on a white background, laced up") turns an invisible image into a usable one.

The Web Content Accessibility Guidelines (WCAG) require alt text for all informative images. Missing alt text is one of the most common WCAG failures found in automated audits, and it is a frequent trigger in ADA-related accessibility lawsuits.

The SEO case

Search engines like Google use alt text to understand and index images. It is a ranking factor for Google Images and Google Lens, and it helps a page rank for relevant visual queries. Well-written alt text that includes natural, descriptive keywords — not keyword stuffing — helps images appear in image search results and rich results.

How to write good alt text

Describe what the image shows in context. Be specific but concise. Do not start with "Image of" — the screen reader already announces it is an image. Include relevant detail a sighted user would take for granted. For purely decorative images, use empty alt text (alt="") so screen readers skip them.

AltGenie automates this by analyzing the image with vision AI and combining it with your page context — title, excerpt, SEO keyword, and taxonomy — to generate alt text that fits the actual page, not just the image in isolation.