G8 — Chapter 7 - Technical SEO

Criterion G8: Canonical Tags — guide + checklist

PART 1 - Fundamentals Chapter 7 - Technical SEO Keyword : balises canoniques

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

Criterion G8 — Canonical Tags 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.

G8 — Canonical Tags (Chapter 7 - Technical SEO): Self-referencing canonical on each page, canonical to preferred version

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 loading time.

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: tool-assisted test (validator / performance). Recommended tool: curl (headers).

  1. Open the page in Chrome → DevTools → Performance/Network tab.
  2. Run WebPageTest and note the main weak point.
  3. Check if the problem repeats on templates.

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

How to fix properly

Strategy: repair, re-crawl, and monitor in Search Console.

  • 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 fashion e-commerce in Paris
  • Before: Lighthouse: 52/100 (heavy JS, unoptimized images).
  • After: Lighthouse: 95/100 (lazy-load, compression, cache).
  • Note: Goal: stabilize INP.

Checklist to tick

  • [ ] Measure before/after
  • [ ] Respects: self
  • [ ] Improvement on template
  • [ ] No CWV regression
  • [ ] Cache and compression OK
FAQ

Frequently asked questions — G8

What is the most common mistake on “Canonical Tags”?

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

Which tool is the fastest for large-scale control?

For this type of criterion, a crawl (e.g. Screaming Frog) plus a targeted check in curl (headers) is generally the fastest combo.

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

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

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