Crawl and index controls
JavaScript rendering
Also called: Client-side rendering, Server-side rendering
JavaScript rendering is the step where a browser runs a page’s JavaScript to build its content; text that only appears after this step is invisible to crawlers that don’t run JavaScript.
In plain words
With server-side rendering, the server sends finished HTML. With client-side rendering, the browser builds the text after loading JavaScript.
Visitors rarely notice the difference. Crawlers that don’t run JavaScript do.
Example
In December 2024, Vercel, a hosting company, published a study of AI crawler traffic on its network. It found that none of the major AI crawlers it measured rendered JavaScript, including GPTBot, ClaudeBot and PerplexityBot, while Google’s Gemini, using Googlebot’s infrastructure, could.
curl -A "GPTBot" https://example.com/your-pageWhy it matters for AI search
If your main text only appears after JavaScript runs, those crawlers may see an almost empty page.
Google says it can process JavaScript as long as it isn’t blocked, but that SEO for sites built on JavaScript frameworks is generally more complex.
What you can do
- Fetch your page with curl, like the command above, and check that your main text is in the response.
- Render important content on the server.
- Run a GEO-Score analysis to check AI crawler access and page structure.
Try it: Analyze a page
Often confused with
- Googlebot
- Googlebot renders JavaScript. In the Vercel study, the other major AI crawlers did not.
Sources
- Vercel (vendor study, December 2024): The rise of the AI crawler
- Google Search Central: Optimizing your website for generative AI features on Google Search
Facts and sources last checked on 19 October 2026.
Related terms
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