Javascript SEO: How Google Crawls, Renders & Indexes JS

This post details research conducted with MERJ to empirically analyze Googlebot's crawling and rendering capabilities for JavaScript-heavy websites. It debunks common myths about Google's ability to render client-side JavaScript, treat JS pages differently, the impact of rendering queue timing, and page discovery speed for JS-heavy sites. The methodology involved using Vercel's Edge Middleware to intercept Googlebot requests and inject a JavaScript library to track rendering completion. Findings indicate that Googlebot successfully renders 100% of analyzed HTML pages on nextjs.org, including those with complex JS, dynamic content, and streamed content via React Server Components. It also confirms that Google treats JS and non-JS pages similarly regarding status codes and meta tags. The research provides recommendations for optimizing modern web apps for SEO.