JavaScript rendering checker
Vercel's 2024 study of AI crawler traffic found GPTBot, ClaudeBot and PerplexityBot don't run JavaScript. GEOFast renders your homepage and up to 3 key pages in a browser and shows how much of their text only appears after scripts run.
- Free
- No account
What the JavaScript rendering checker checks.
- 01
Fetches each page as a crawler does
The HTML your server sends, with no scripts run.
- 02
Renders it in a real browser
The same page after JavaScript has run, as a visitor sees it.
- 03
Compares the text
It measures how much of the visible text exists only in the rendered page.
- 04
Gives each page a verdict
Over 10% of the text from JavaScript is at risk; over 40% is invisible to crawlers that skip scripts.
What each verdict means.
- Readable
AI crawlers see the same text as your visitors.
- At risk
More than 10% of the page's text only appears after JavaScript runs.
- Invisible
More than 40% of it does: most of the page doesn't exist for those crawlers.
- Not measured
We couldn't render the page in a browser this time.
Numbers from our own scans.
In our test run on 30 well-known sites on October 5, 2026, 5 had pages whose text depended on JavaScript, the most common real finding among well-run sites.
Questions about the JavaScript rendering checker.
Do AI crawlers run JavaScript?
Vercel's 2024 study of AI crawler traffic found GPTBot, ClaudeBot and PerplexityBot reading the HTML your server sends without running scripts, so text that JavaScript adds is invisible to them. Googlebot renders JavaScript for Google Search. Which crawlers render
How do I fix content that needs JavaScript?
Send the text in the HTML: server-side rendering or static generation in frameworks like Next.js, Nuxt or Astro, or prerendering for a single-page app. The report's fix gives the steps for your stack.
Which pages does it test?
Your homepage and up to 3 key pages the crawl finds, each rendered in a real browser.
What counts as at risk?
More than 10% of a page's text appearing only after JavaScript runs is at risk; more than 40% is invisible to crawlers that skip scripts.
Is the JavaScript rendering checker free?
Yes. It's part of GEOFast's free X-ray: no account, nothing to install, and most X-rays finish in under a minute.
Keep reading
- GEOFast MCP server for ChatGPT, Claude and coding agentsConnect ChatGPT, Claude, Claude Code, Cursor or any MCP client to your AI visibility results, fixes and briefs, and let it edit prompts when you allow.
- Why doesn't ChatGPT show your website?Six reasons ChatGPT leaves a site out, in the order to check them: robots.txt, firewalls, noindex, JavaScript, Bing's index and who the pages it reads name.
- Do AI crawlers render JavaScript?Google's and Bing's crawlers render JavaScript. OpenAI, Anthropic and Perplexity don't say, and Vercel's 2024 study found theirs don't. Our data on cited pages.
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- GEO auditA free GEO audit of up to 300 pages: AI crawler access, JavaScript rendering, 21 checks and fixes ranked by impact, with code. No sign-up.
Find out what AI says about your site.
Paste your URL and leave with a ranked list of what to fix, with steps and code.
- Free
- No account