JavaScript rendering
The execution of a page's client-side JavaScript by a search engine so that content and links generated at runtime become indexable.
Crawling IndexingRendered HTML
DOM (Document Object Model)
The in-memory tree representation of a document that the browser builds from HTML and mutates with JavaScript; the rendered DOM is what search engines index.
In full
The source HTML delivered by the server and the DOM after scripts run can differ dramatically, tags injected, canonicals rewritten, content replaced. For SEO the practical rule is that the rendered DOM wins, but only for engines that render; anything relying on scripts is invisible to non-rendering agents. Comparing view-source HTML with the rendered DOM in URL Inspection is the standard diagnostic for JavaScript indexing problems.
Example
View-source shows no meta description, but the rendered DOM contains one injected by a tag manager, Google may use it, while a simple HTML-only crawler will not.
Related terms
Render queue
The deferred queue in which Google executes a page's JavaScript with a headless Chromium instance after the raw HTML has already been…
Hydration
Attaching client-side JavaScript behaviour to server-rendered HTML so a static page becomes interactive.
Prerendering
Generating and caching a fully rendered HTML snapshot of a JavaScript page at build time or on request, so crawlers receive complete markup.
URL Inspection tool
A Search Console feature showing Google's indexed state for a URL plus a live test with rendered HTML, screenshot, and page resource…