Technical GEO
AI crawlers don't execute JavaScript — why server rendering is the precondition of GEO | Suparanku
Major AI crawlers — GPTBot, ClaudeBot and peers — do not execute JavaScript. Vercel's early-2025 analysis of more than half a billion GPTBot requests found no traces of JS execution. Content that appears only after client-side rendering is invisible to AI, making server-rendered HTML the technical precondition of GEO.
What we actually know
Vercel, together with MERJ, analyzed AI-crawler traffic across its network. As of early 2025, GPTBot alone generated over half a billion requests per month, and the conclusion was unambiguous: zero traces of JavaScript execution. GPTBot sometimes downloads JS files (about 11.5% of requests) but never runs them. ClaudeBot and PerplexityBot behave the same way.
ChatGPT citations are powered by the retrieval bots OAI-SearchBot and ChatGPT-User, while GPTBot is a training scraper. Blocking GPTBot only affects model training; blocking OAI-SearchBot removes your site from ChatGPT answers. Allow/deny rules and CDN checks must cover the retrieval bots, not just GPTBot.
A page rendered purely client-side in React or Vue is, to an AI crawler, mostly empty HTML. If your product description and pricing only appear after hydration, they feed neither training nor answer generation.
Check your site in three minutes
- Disable JavaScript in your browser’s dev tools and reload key pages (product, pricing, company). If the content is visible, you are server-rendered.
- Or right-click → “View page source” and confirm the body text exists in the source HTML. A bare
<div id="root"></div>is the warning sign. - Check your CDN/WAF settings as well. Even with AI bots allowed in robots.txt, some CDNs block them by default — a common hidden cause — an Otterly analysis of more than a million AI citations found 73% of sites have technical barriers blocking AI crawlers.
Your options
- Static generation (SSG) — first choice for content sites: HTML is complete at build time, which wins on crawlers, speed and operations. This site works this way.
- Server-side rendering (SSR) — for pages that need real-time data; the server returns HTML per request.
- Isolate interactivity — instead of a full SPA, run only the widgets that need it on the client (islands architecture) so the body text always stays in static HTML.
Google’s classic search can render JavaScript, but Google itself lists crawlability and indexability as preconditions for its AI features too. Since December 2025, however, Google excludes non-200 pages (redirects and errors) from its rendering pipeline entirely — client-side JS on those pages is invisible even to Google. Server rendering is the safe choice across every platform.
Summary
Most GEO advice focuses on what to write. Before that comes a technical gate: can AI see what you wrote at all? Body text visible with JavaScript off, and a CDN that isn’t silently blocking AI bots — verifying these two things is the starting point of every GEO effort.
Related terms: AI crawler, RAG, GEO