Official statement
Other statements from this video 19 ▾
- 27:21 Pourquoi vos Core Web Vitals mettent-ils 28 jours à se mettre à jour dans Search Console ?
- 36:39 Faut-il vraiment tester ses Core Web Vitals en laboratoire pour éviter les régressions ?
- 98:33 Les animations CSS pénalisent-elles vraiment vos Core Web Vitals ?
- 121:49 Les Core Web Vitals vont-ils encore changer et comment anticiper les prochaines mises à jour ?
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- 203:58 Faut-il vraiment commencer petit pour débloquer son crawl budget ?
- 228:24 Faut-il vraiment régénérer vos sitemaps pour retirer les URLs obsolètes ?
- 259:19 Pourquoi Google refuse-t-il de fournir des données Voice Search dans Search Console ?
- 295:52 Comment forcer Google à rafraîchir vos fichiers JavaScript et CSS lors du rendering ?
- 353:48 Faut-il vraiment renseigner les dates dans les données structurées ?
- 390:26 Faut-il vraiment modifier la date d'un article à chaque mise à jour ?
- 432:21 Faut-il vraiment limiter le nombre de balises H1 sur une page ?
- 450:30 Les headings ont-ils vraiment autant d'importance que le pense Google ?
- 555:58 Les mots-clés LSI sont-ils vraiment utiles pour le référencement Google ?
- 585:16 Combien de liens par page faut-il pour optimiser le PageRank interne ?
- 674:32 Les requêtes JSON grèvent-elles vraiment votre crawl budget ?
- 717:14 Faut-il vraiment bloquer les fichiers JSON dans votre robots.txt ?
- 789:13 Google peut-il deviner qu'une URL est dupliquée sans même la crawler ?
Google emphasizes: every old URL must point to its new destination through comprehensive mapping, and all internal signals (rel canonical, navigation, footer) must point to the new URLs. Without this traceability work, canonicalization fails and the engine inherits conflicting signals. In practical terms, a migration without rigorous mapping exposes you to lasting ranking losses and toxic redirect chains.
What you need to understand
Why does Google put so much emphasis on URL mapping during migration? <\/h3>
Because the engine inherits your mistakes <\/strong>. When you migrate a site, Googlebot must understand that URL A has become URL B — and that this is not a duplicate, nor a temporary change, nor a 404 error. Comprehensive mapping (tracking each old URL to its new destination) provides the necessary consistency for canonicalization <\/strong>.<\/p> Without rigorous mapping, you multiply conflicting signals: an old backlink points to \/old-page, but your XML sitemap lists \/new-page, and your internal linking mixes the two. The engine no longer knows which version to index <\/strong>, so it fumbles — and while it fumbles, your traffic collapses.<\/p> Google doesn't settle for 301 redirects. It observes the consistency of all your signals <\/strong>: rel canonical, links in the main navigation, footer, breadcrumb, XML sitemap, pagination, hreflang for multilingual, alternate tags for mobile, contextual links within the content. Each signal must point to the new canonical URL.<\/p> This is where it often gets tricky. You set up a perfect 301, but the rel canonical remains stuck on the old URL — conflicting signal <\/strong>. Or you forget to update the footer that contains 50 links, resulting in 50 opportunities to confuse the bot. Consistency is the cornerstone.<\/p> Canonicalization is the process by which Google chooses which version of a URL to index and display in the SERPs when multiple versions exist. If all your internal signals converge towards a single version <\/strong>, the choice is obvious — the engine doesn’t waste time hesitating.<\/p> In contrast, divergent signals (redirects, canonicals, internal links) create internal competition. Google has to arbitrate — and its arbitration may not be what you want. Worse, during this arbitration period, PageRank fragments <\/strong> across competing versions.<\/p>What do we mean by 'all internal signals'? <\/h3>
How does this practice facilitate canonicalization? <\/h3>
SEO Expert opinion
Is this statement consistent with observed practices in the field? <\/h3>
Yes, and it is even one of the few Google statements perfectly aligned <\/strong> with what we observe in production. The failed migrations I deal with almost always have the same patterns: partial mapping (only the “important” pages), redirects set up and then forgotten, internal signals never updated. The result: 30-50% loss in organic traffic within 3 months <\/strong>.<\/p> The problem is that we underestimate the volume of details. A site with 10,000 pages can easily generate 50,000 indexed URLs if you count URL parameters, paginations, filters. Mapping “the main pages” ignores 80% of crawl budget and backlinks — and leaves the engine in the dark <\/strong>.<\/p> Google does not specify the processing time. A clean migration with comprehensive mapping and consistent signals can still see a fluctuation of 2-4 weeks <\/strong> while the engine recrawls everything. This is normal — but it panics clients who see their traffic oscillate. [To be verified] <\/strong>: Google does not provide any numerical data on the average stabilization time post-migration.<\/p> Another nuance: some pages may intentionally have no new destination — they are removed. In this case, a 404 or 410 is preferable to a generic 301 redirect to the homepage <\/strong>. Google tolerates this, but you need to acknowledge it in the mapping (column “status” = 404) and compensate with internal linking to substitute content.<\/p> If your new site suffers from independent structural issues <\/strong>: crawl blocked by robots.txt, new URLs not indexable (accidental noindex), catastrophic Core Web Vitals, broken internal linking. Perfect mapping is useless if the new site is technically flawed — Google indexes the new URLs but rankings collapse <\/strong>.<\/p> Another case: you migrate from domain A to domain B, but domain B has a toxic history (manual penalty, past spam). Redirects may pass juice, but the reputation of the target domain drags everything down <\/strong>. Before migrating, check the history of the destination domain in Search Console and via third-party tools (Wayback Machine, Ahrefs to see historical backlinks). <\/p>What nuances should be added to this recommendation? <\/h3>
In what cases might this rule still fail? <\/h3>
Practical impact and recommendations
What should you do specifically before and during the migration? <\/h3>
First of all, build a comprehensive mapping table <\/strong>: old URL | new URL | HTTP status | content type | priority. Crawl your current site with Screaming Frog or Oncrawl to capture all indexed URLs, including those discovered via server logs. Cross-reference with URLs in Search Console (Coverage) and backlinks (Ahrefs, Majestic). <\/p> Then, implement 301 redirects in a rules file (htaccess, nginx.conf, server middleware) testing each redirect manually or via a Python script. Ensure there are no redirect chains <\/strong> (A → B → C) — Google follows up to 5 hops but PageRank dilutes with every step.<\/p> The classic mistake: updating the XML sitemap but forgetting the internal linking. The result is that your pages bounce between old and new URLs <\/strong>, creating fragmentation of internal PageRank. Another trap: hard-coded URLs in templates (footer, sidebar) that developers forget to parameterize dynamically.<\/p> Never underestimate poorly configured rel canonicals <\/strong>. A CMS that automatically generates a canonical to the current URL can point to the old URL if you haven’t updated the base URL parameters. Crawl the new site in pre-production and filter the canonicals to ensure none points to the old domain.<\/p> Crawl the site in production 48 hours after going live. Filter for 3xx status codes in chains <\/strong>, 4xx, 5xx. Extract all rel canonicals and hreflang to check that they point to the new domain. Inspect server logs to see if Googlebot encounters errors (timeouts, 500, 503). <\/p> Monitor in Search Console the graphs of Index Coverage <\/strong>: the old URLs should gradually disappear (status “Redirected”) while the new ones appear (“Indexed”). If after 2 weeks the old URLs remain predominant, it means a conflicting signal persists — find out where.<\/p>What mistakes should you absolutely avoid when updating internal signals? <\/h3>
How can you check that the site is compliant after migration? <\/h3>
❓ Frequently Asked Questions
Faut-il rediriger toutes les URLs ou seulement les pages importantes ?
Peut-on utiliser des redirects 302 temporaires pendant une migration ?
Combien de temps faut-il pour que Google indexe entièrement le nouveau site ?
Que faire si des anciennes URLs restent indexées plusieurs semaines après la migration ?
Faut-il conserver les redirects 301 indéfiniment après la migration ?
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