What is prerender?
Prerender is an HTML rendering service for JavaScript sites. Prerender.io says its crawler fetches a customer's pages so the service can render and cache them for search engines and AI crawlers. A request from Prerender is the cache-building step, not proof that a downstream search or AI system requested the same page.
The service uses desktop and mobile crawlers backed by a headless browser, plus a sitemap worker. Current full user agents contain Prerender (+https://github.com/prerender/prerender), while the sitemap worker can consist of that identifier alone. Browser version numbers change, so matching the stable Prerender text is more durable than matching a complete header.
Rendered HTML can help a crawler read a page that otherwise returns a thin JavaScript shell. That is an indirect delivery function: Prerender itself does not rank the page, choose citations, or operate a public answer index. Its crawler documentation also makes no claim that an origin fetch supplies general model-training data.
Prerender.io's current crawling guidance says the service respects robots.txt, but this directory record does not mark that behavior as confirmed. The operator also warns that user-agent strings can be copied. It publishes methods based on current IP ranges and forward-confirmed reverse DNS for customers that need to verify requests.
