Technical SEO · Advanced

JavaScript SEO

JavaScript SEO is making sure pages built with JavaScript can be crawled, rendered and indexed. Google can render JavaScript, but it takes extra time, and most AI crawlers don't run it at all.

By Thryv StudioUpdated

Level
Advanced
Google
Renders JavaScript with an up-to-date Chromium
Most AI crawlers
Read only the HTML the server sends
Safest approach
Server-side rendering or static HTML

What is JavaScript SEO?

Many modern sites send a nearly empty HTML page and build the content in the browser with JavaScript. Humans see the finished page; crawlers may not. JavaScript SEO covers the choices and fixes that make the content visible to them.

How search engines and AI crawlers handle it

  • Google crawls the HTML, then renders the page in a headless Chromium to see JavaScript content. Rendering can be delayed, and errors can hide content.
  • Most AI crawlers, including those behind ChatGPT, Claude and Perplexity, read the HTML without running scripts. Content that only appears after JavaScript runs is invisible to them.

Best practices

  1. Render main content on the server or at build time.
  2. Use real <a href> links for navigation.
  3. Put titles, meta tags, canonicals and structured data in the initial HTML.
  4. Test what crawlers see by viewing the raw HTML, not the rendered page.

Frequently asked questions

Is a React or Next.js site bad for SEO?

Not if the content is rendered on the server or at build time. Client-only rendering is the risk.

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