Definition

JavaScript SEO is the branch of technical SEO concerned with how search engines process JavaScript-driven content. It covers the crawl, render and index pipeline that Google applies to client-rendered pages, single-page applications and progressively enhanced sites.

Google processes JavaScript in three phases — crawling, rendering and indexing — and rendering is deferred until resources are available. That delay means content injected by JavaScript may take longer to appear in search results than HTML-rendered content. JavaScript SEO concerns include serving meaningful HTTP status codes, using the History API for routing rather than fragment identifiers, providing unique titles and meta descriptions per route, exposing content without requiring user interaction, and ensuring rendered markup includes the structured data and internal links Google needs.

Examples

• Single-page application route handling

  A React app uses the History API so each route has a unique URL like `/products/runner` rather than `/#/products/runner`. Googlebot can crawl, render and index each route as a distinct page.

• Content hidden behind a click

  A site loads product specifications only after the user clicks a 'Show details' button. Because Googlebot does not interact with the page, the specs are absent from the rendered HTML and do not appear in the indexed copy.

Sources

• Google Search Central — Understand the JavaScript SEO basics

Related terms

• Server-Side Rendering
  A rendering strategy in which the server generates a page's full HTML on each request, rather than leaving the browser to build it with client-side JavaScript.
• Dynamic Rendering
  Serving a pre-rendered HTML version of a page to crawlers while delivering a client-rendered version to human visitors of the same URL.
• Indexing
  The process by which a search engine analyses a fetched page and stores information about it so the page can later be returned in search results.
• Render-Blocking Resources
  Resources — typically CSS and synchronous JavaScript — the browser must fetch and parse before it can paint the first frame of a page.
• Core Web Vitals
  A set of three Google metrics that measure real-world page experience: loading speed, interactivity and visual stability.

Where QueryCatch uses this

• SEO Audit
• Page Optimisation