How Google Handles JavaScript Throughout the Indexing Process

Understanding how search engines like Google crawl, render, and index web pages is key for optimizing sites for search engines. Over time, Google has changed its processes, making it challenging to keep up, especially with client-side JavaScript.

Common myths persist in the community, such as "Google can't render client-side JavaScript" and "JavaScript-heavy sites have slower page discovery."To address these myths, Vertify partnered with MERJ, an SEO consultancy, to conduct experiments on Google’s crawling behavior. They analyzed over 100,000 Googlebot fetches to validate Google's SEO capabilities.

Evolution of Google's Rendering

Google's rendering capabilities have evolved significantly:

• Pre-2009: Limited JavaScript support, focusing on static HTML.

• 2009-2015: AJAX crawling scheme allowed HTML snapshots of dynamic content.

• 2015-2018: Early JavaScript rendering with a headless Chrome browser.

• 2018-present: Modern rendering using the latest Chrome version, supporting advanced JavaScript features.

Debunking Common Myths

1.Google can't render JavaScript content:

Tests showed Google can fully render JavaScript-heavy pages, including those with dynamic content and React Server Components.

2.Google treats JavaScript pages differently:

Analysis confirmed no significant difference in how Google processes JavaScript-heavy pages versus static HTML pages.

3.Rendering queue and timing significantly impact SEO:

Most pages are rendered within minutes, debunking the idea of long rendering queues.

4.JavaScript-heavy sites have slower page discovery:

Google can discover and crawl links in rendered pages and non-rendered JavaScript payloads, showing no inherent disadvantage for JavaScript-heavy sites.