G20 — Chapter 7 - Technical SEO

Criterion G20 : JavaScript SEO-friendly — guide + checklist

PART 1 - Fundamentals Chapter 7 - Technical SEO Keyword : javascript seo-friendly

This is typically the kind of detail that prevents conflicting signals.

The criterion **G20 — JavaScript SEO-friendly** is part of our SEO checklist (335 criteria). Here, you have a **practical** method to check and fix it — with a concrete example.

What exactly this criterion covers

This is typically the kind of detail that prevents conflicting signals.

**G20 — JavaScript SEO-friendly** (Chapter 7 - Technical SEO): SSR or pre-rendering recommended, content accessible without JS

Why it matters (SEO + UX)

Why it matters: it is a safeguard against duplicate content / cannibalization. When poorly applied, we often observe: ambiguity (wrong associated query), duplication between pages, or loss of performance on impressions.

On high-volume generated sites, this criterion also serves as a **safeguard**: a stable rule prevents 1,000 errors at once.

How to check (step by step)

Approach: validation via Search Console (real data). Recommended tool: **PageSpeed Insights**.

  1. Open the page in Chrome → DevTools → Performance/Network tab.
  2. Run PageSpeed Insights and note the main weakness.
  3. Check if the issue repeats on “money” pages.

Tip: first isolate 10 “representative” URLs (top pages + generated pages) before scaling the fix.

How to fix properly

Strategy: fix + add a safeguard for bulk import.

  • Fix the biggest cost source (images, JS, fonts, cache).
  • Retest, then apply to the template (not page by page).
  • Add a safeguard: weight budget (KB) and CI check if possible.

Then: re-crawl 50–200 URLs, then monitor Search Console for 7–14 days (impressions/CTR/indexing).

Concrete example (illustrative)

Example (illustrative):

  • **Context**: training page for insurance in Marseille
  • **Before**: Lighthouse: 25/100 (heavy JS, unoptimized images).
  • **After**: Lighthouse: 93/100 (lazy-load, compression, cache).
  • **Note**: Goal: stabilize INP.

Checklist to tick

  • [ ] Measure before/after
  • [ ] Respects: SSR or pre-render
  • [ ] Improvement on template
  • [ ] No CWV regression
  • [ ] Cache and compression OK
FAQ

Frequently asked questions — G20

What is the most common mistake on “JavaScript SEO-friendly”?

Fixing an isolated page without fixing the template/import: the error returns on the next generation.

Which tool is fastest for large-scale checking?

For this type of criterion, a crawl (e.g. Screaming Frog) + targeted verification in PageSpeed Insights is generally the fastest combo.

How to prevent this from recurring on 10K generated pages?

Freeze an auto-generation rule (title/structure/schema/URLs) + add automatic control (crawl or test) before production import.

Ready to go from theory to action?

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