JavaScript & SPA SEO
The modern web is built on JavaScript, but search engines and AI bots still prefer HTML. 42crawl helps you bridge this gap by auditing your Single Page Applications (SPA) and client-side rendered content to ensure maximum visibility in the era of generative engine optimization.
The Rendering Gap
Many modern sites (built with React, Vue, or Angular) serve an empty HTML "shell" and rely on JavaScript to fetch and display content. This creates several technical SEO risks:
- Two-Pass Indexing: Google may index your empty shell first and only render the content days or weeks later.
- Crawl Budget Depletion: Rendering JS is expensive. Bots may crawl fewer pages if your site is script-heavy.
- Hidden Links: If your links are handled by JS instead of standard
<a>tags, an SEO crawler may never find them.
What 42crawl Audits
We analyze the "First Look" of your site to determine how dependent your content is on JavaScript execution.
1. Visible Text vs. Script Size
We calculate the ratio of indexable text in the raw HTML compared to the size of your JS bundles. If your content is "thin" until scripts run, your GEO optimization performance will suffer.
2. Framework Detection
We automatically identify if you're using Next.js, Remix, Nuxt, or Gatsby. We check if you're taking advantage of Server-Side Rendering (SSR) or Static Site Generation (SSG).
3. JavaScript-Only Links
We flag any internal links that lack a proper href attribute, as these are invisible to most crawlers and AI bots, leading to orphaned pages.
Best Practices for JS SEO
- Server-Side Rendering (SSR): This is the gold standard. It provides full HTML to bots while maintaining the fast SPA experience for users.
- Metadata Presence: Ensure your Title Tags and Meta Descriptions are present in the raw HTML source, not just injected via JS.
- Monitor Core Web Vitals: Heavy JS bundles are the #1 cause of poor INP (Interaction to Next Paint) and LCP scores. Use our Performance Analysis to find the bottlenecks.
Using the JS SEO Report
In the Technical tab of your 42crawl dashboard, look for the JavaScript section. We provide a "Dependency Score" that tells you how much of your SEO value is locked behind code.
Ready to audit your SPA?
- Run a crawler audit today.
- Check your Internal Link health.
- Read our blog post on SPA SEO.