What exactly this criterion covers
This is typically the kind of detail that prevents conflicting signals.
**L18 — Declared Page Language** (Chapter 12 - UX & Accessibility): <html lang=fr> mandatory for screen readers
L18 — Chapter 12 - UX & Accessibilité
Criterion L18 : Declared Page Language — guide + checklist
This is typically the kind of detail that prevents conflicting signals.
The **L18 — Declared Page Language** criterion is part of our SEO checklist (335 criteria). Here, you have a **practical** method to check and fix it — with a concrete example.
Why it matters (SEO + UX)
Why it matters: it is a lever for CTR and perception in SERP. When poorly applied, we often observe: ambiguity (wrong associated query), duplication between pages, or loss of performance on Core Web Vitals.
On 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: check during crawl (list + export). Recommended tool: **Lighthouse**.
- Open the page in Chrome → DevTools → Performance/Network tab.
- Run PageSpeed Insights and note the main weak point.
- Check if the problem repeats on mass-generated pages.
Tip: first isolate 10 “representative” URLs (top pages + generated pages) before scaling the fix.
How to fix properly
Strategy: fix, re-crawl, and monitor in Search Console.
- Simplify the mobile journey (visible menu/CTA, no aggressive popups).
- Fix instabilities (CLS) and interactivity (INP) if affected.
- Test on 2–3 screen sizes and re-measure.
Then: re-crawl 50–200 URLs, then monitor Search Console for 7–14 days (impressions/CTR/indexing).
Concrete example (illustrative)
Example (illustrative):
- **Context**: comparison page for restaurant in Rabat
- **Before**: Confusing menu on mobile + hidden CTA + visible CLS.
- **After**: Simplified navigation + visible CTA + visual stability.
- **Note**: Goal: readability + engagement (which indirectly helps SEO).
Checklist to tick
- [ ] Mobile first
- [ ] CTA visible
- [ ] No major friction
- [ ] Visual stability OK
FAQ
Frequently asked questions — L18
What is the most common mistake on “Declared Page Language”?
Applying an automatic pattern too generic (same logic on all pages) without adding a differentiating element.
Which tool is fastest for large-scale control?
For this type of criterion, a crawl (e.g. Screaming Frog) + targeted verification in Lighthouse is usually 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?
Validate this criterion with an audit, then deepen the method in the Academy.