JavaScript rendering is the process by which a page's content is not created on the server but only in the browser, by running a script. Search engines can handle this, but with delay and not always completely – rendering happens in a second wave, after the initial crawl. Language models and tools that load a page just once generally don't run scripts at all, so they see an empty shell. Checking this is simple: look at the page's source code without the script running and search it for headings, text, and links. If they aren't there, the content is at risk. The solution is to render key content on the server or use page pre-generation, or at least ensure that the base code contains headings, the main text, and navigation links as regular links.
See also: Crawl budget, AI Crawler, Click depth.
