Picture alt text

TL;DR

Alt text is the short written description you add to an <img> tag so AI crawlers, search engines, and screen readers can understand what the image shows. Prerender scores every page on whether your images carry alt text — you gain points for each image that has it, and lose points for images that don't. Adding accurate, concise alt text to every meaningful image is one of the fastest ways to improve both accessibility and your AI & search visibility.

Why image alt text matters for AI & search visibility

AI crawlers and search engines can't see images the way your website visitors can. They rely on the alt attribute to understand what each image represents, how it relates to the surrounding content, and whether the page is worth citing or ranking.

When alt text is missing, three things happen:

• AI crawlers may miss or misread the context of your page.
• Search engines lose a signal they use to rank image and page results.
• Website visitors using screen readers can't access the content.

Alt text is a small change with outsized impact — it improves AI citations, search rankings, and accessibility at the same time.

How Prerender scores image alt text

Prerender checks every <img> tag on your rendered pages and applies the following scoring rules:

The cap on missing alt text means a single page with many broken images won't completely tank your score — but it also means the fastest way to recover points is to fix the missing alt attributes first.

Example: well-formed image alt text

Each of these images carries clear, descriptive alt text that an AI crawler can read and use:

<img src="example.jpg" alt="A beautiful sunset over the ocean">
<img src="illustration.png" alt="Illustration of growth chart">
<img src="photo.jpg" alt="Portrait of a happy family">

Best practices for writing alt text

Use these rules when adding or rewriting alt text across your site:

• Be descriptive but concise. Aim for a short sentence that conveys what the image shows and why it's on the page. Avoid stuffing keywords.
• Reuse text when images are identical. If the same image appears multiple times for the same purpose, use the same alt text — don't invent new descriptions for each one.
• Use empty alt for decorative images. If an image is purely decorative and adds no meaning, write alt="". This tells AI crawlers and screen readers to skip it, which is the correct behavior for decorative graphics.
• Don't confuse alt with title. The title attribute shows a tooltip on hover, but it isn't read by screen readers and carries far less weight for AI crawlers and search engines. Alt text is what matters for visibility.

How to fix missing alt text

Run a render on the page in your Prerender dashboard and check the SEO score breakdown. Any image flagged as missing alt text is listed with its src URL, so you know exactly which tags to update in your codebase or CMS.

Once you've added alt text and redeployed, the next render will pick up the change and your score will update on the following cache refresh.

Related articles

• • How this feature works — see how Prerender's scoring engine evaluates your pages overall.
  • Open Graph Protocol — visibility on social media
  • Meta description — another high-impact element AI crawlers and search engines rely on.
  • Title element — how Prerender scores your page titles for AI & search visibility.