Image Alt Text

One attribute, three very different readers

Alt text usually gets filed as an accessibility checkbox, and that undersells it badly. Three distinct consumers read that attribute, and they read it differently.

Screen readers announce alt text in place of the image. If the attribute is missing entirely, most screen readers fall back to the filename, so a real person hears "IMG underscore 4382 dot jpg" in the middle of your article. An empty alt="", on the other hand, tells the screen reader to skip the image completely, which is exactly right for decoration. Missing and empty are not the same thing, and mixing them up is the most common alt text mistake I see in audits.

Search engines use alt text as a primary signal for image search and as context for the surrounding page. Google's own image SEO documentation lists alt text alongside filenames and structured data as the inputs it uses to understand image content. For product, recipe, how-to, and local queries, image results and image packs carry real traffic, and pages with empty image metadata simply do not compete there.

AI crawlers. This is why the check sits in our GEO category. Bots like GPTBot, ClaudeBot, and PerplexityBot fetch your HTML as text. Running vision models over every embedded image at crawl scale is expensive, so in practice the text in your markup, alt attributes included, is what reliably makes it into the systems generating answers about your pages. If a fact only exists in pixels, for most AI retrieval purposes it does not exist.

The thirty-second decision tree

What good alt text sounds like

Describe the image the way you would to a colleague on the phone who needs to act on it. Context decides content: the same photo of a running shoe needs "Nike Pegasus 41 in white and volt, side profile" on a product page, and maybe nothing at all when it is a mood shot in a training article. Front-load the important words, skip "image of" and "picture of" because the screen reader already announces the role, and keep it tight. The old advice to stay near 125 characters is not a hard technical limit in modern screen readers, but it remains a good instinct: if your alt runs three lines, the detail belongs in the body copy.

The GEO angle, without the hype

Answer engines build responses from crawled text. When an assistant summarizes your product page or cites your comparison chart, everything the image communicates has to exist somewhere in the markup for it to survive the trip. Alt text is the image's proxy in that pipeline, so entity-rich, factual alt ("DJI Mini 4 Pro folded next to a smartphone for scale") gives retrieval systems usable facts, while "drone photo new best 2024" gives them nothing. The discipline is the same one accessibility has demanded for twenty-five years, the stakes just got higher. I would not chase any exotic AI-specific alt formula; I would make sure every fact your images carry also exists as text, in alt, captions, or nearby prose.

How to audit alt text at scale

Screaming Frog is the workhorse: crawl the site, open the Images tab, and work the Missing Alt Text, Missing Alt Attribute, and Alt Text Over 100 Characters filters. Bulk Export, then Images, then Images Missing Alt Text Inlinks gives you a spreadsheet mapping every offending image to the pages that embed it. Sitebulb surfaces the same data with friendlier reporting if you prefer that. axe DevTools catches the subtler per-template failures, like images whose alt exists but says "image" or repeats the filename. And Search Console tells you where to start: switch performance to Search type: Image and prioritize the templates that already earn image impressions.

One WordPress gotcha worth knowing: alt text saved in the media library is copied into content at insert time. Updating the library later does not update images already sitting in published posts, so fix alt where the image is embedded, not just in the library.

A fix workflow that actually finishes

1. Crawl and segment by template. Product images, blog heroes, thumbnails, and theme icons each need different treatment, and lumping them together kills momentum.
2. Kill the decorative noise first. Spacer graphics, borders, and theme flourishes get alt="" in template code. One fix can clear thousands of warnings.
3. Write real alt for the money images: products, step-by-step screenshots, charts. This is where the search and GEO value lives.
4. Make alt a required field in the CMS workflow with a one-line style guide, so the backlog never regrows.
5. Use AI generation as a first draft, not a final answer. Bulk vision-model alt is a fine starting point, but someone who knows the page context has to approve, because the model does not know your product names or why the image is there.
6. Re-crawl and compare counts. If missing-alt numbers do not drop to near zero, a template is still emitting bare img tags.

Questions that come up