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The AltTextLab web snippet is a JavaScript embed that detects images without alt text on each page load and generates descriptions for them automatically.

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How it works

  1. You add one <script> tag to your site’s <head>
  2. On the first visit to any page, the snippet detects images missing alt text and submits them for generation
  3. Generated alt text is cached on a CDN — every subsequent visit gets the result instantly
Alt text is generated once per image. The CDN cache means no repeated processing and no impact on page load performance.

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Key properties

Non-blocking — the snippet loads asynchronously using the defer attribute. It never blocks page rendering — your content loads normally while the script processes images in the background. Lightweight — the script is optimized for modern browsers and adds negligible overhead to your site’s resources. It does not interfere with existing scripts or styles. CDN-delivered — once alt text is generated for an image, it is cached in a global CDN and delivered in milliseconds on every subsequent page view, even under high traffic. Privacy-safe — the snippet processes only public image URLs to generate alt text. No visitor data is collected or stored. SEO-safe — alt text is applied to alt attributes directly in the DOM. Search engines index it the same way they would static markup, with no negative SEO impact. Scalable — whether your site has dozens of images or millions of assets, the architecture handles traffic spikes without bottlenecks.
When connecting a new site with a large existing media library, there may be an initial delay while the system processes all images for the first time. Every image will be processed — once cached in the CDN, alt text is delivered instantly on all subsequent visits.

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Requirements

An active AltTextLab subscription is required. Without one, new images will not receive generated alt text.

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Next steps

Get started

Create your first web snippet in the dashboard.

Installation

Embed the script and configure parameters.

Ignoring decorative images

Skip icons, spacers, and other non-content images.