JavaScript SEO
The practice of ensuring search engines can properly crawl and index content generated or modified by JavaScript.
The JavaScript rendering challenge
Search engines must execute JavaScript to see content that loads client-side. While Google can render JavaScript, it requires significantly more resources than reading static HTML. This creates delays—pages may be crawled but not rendered and indexed for days or weeks.
Other search engines like Bing handle JavaScript less reliably. If your critical content—headings, body text, navigation—requires JavaScript execution to appear, some crawlers simply won't see it. This invisibility kills SEO potential.
Common JavaScript SEO problems
Single-page applications built with React or Vue often load an empty HTML shell, then fetch and render everything via JavaScript. Search engines see the shell, not the content. This requires server-side rendering or static generation to fix.
Infinite scroll, lazy-loaded content, and JavaScript-dependent navigation create discovery problems. If links only appear after JavaScript executes, crawlers may never find linked pages. Internal linking fails when links don't exist in HTML.
Client-side routing changes URLs without full page reloads. Poorly implemented, this confuses crawlers about canonical URLs and page structure. History API usage requires careful technical implementation.
Testing JavaScript SEO
View source (not inspect element) to see what HTML crawlers receive initially. If critical content is missing, it requires JavaScript rendering to appear—a problem for SEO.
Google Search Console offers URL inspection tool showing how Google renders your pages. Compare the rendered version to source HTML. Significant differences indicate JavaScript dependency that may delay indexing.
The Astro advantage
Astro generates static HTML at build time. All content, navigation, and links exist in HTML before JavaScript runs. Search engines see complete pages immediately—no rendering required, no indexing delays.
This architectural choice eliminates JavaScript SEO challenges entirely. Interactive components can still use JavaScript, but critical content remains in HTML. Best of both worlds: fast, accessible, and perfectly crawlable.
Related terms
Why it matters
Understanding “JavaScript SEO” helps you speak the same language as our design and development team. If you need help applying it to your project, book a Fernside call.