ChatGPT, Claude and Perplexity's fetchers don't run JavaScript, leaving client-rendered sites invisible to AI
gaganghotra_ · x · 2026-11-02
SEO expert Suganthan warns that while Google renders JavaScript, the live fetchers of ChatGPT, Claude and Perplexity don't execute it. Heavily client-rendered sites show AI crawlers only the nav, footer and cookie banner — while browsers and Google rankings make everything look fine.
He launched a free tool, JS Rendering Gap Checker, which:
- Fetches the URL raw with ChatGPT-User's user agent (no JS executed)
- Renders the same URL in a headless browser
- Runs both through the same text extractor (so it compares renderers, not converters) and scores the share of body copy the raw fetch misses, measured in characters; blocks under 25 chars are excluded
- Thresholds: >70% missing means the page is effectively a shell, >30% most is gone, >8% some is missing
His advice: check page by page, since marketing pages and app routes can behave very differently.
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