Does a domain migration really transfer all ranking signals?

What does Google mean by 'simple domain migration'?

Google refers here to a one-to-one migration, which is the case where each URL from the old domain finds a direct match on the new domain. The architecture remains unchanged; only the domain name evolves. No redesign, no change in URL structure, no merger with another site.

This is the cleanest scenario: example.com/seo-article becomes example-new.com/seo-article via a permanent 301 redirect. Google can then interpret the migration as a mere change of address, with no ambiguity about what replaces what.

Which ranking signals are supposed to be transferred?

When Mueller speaks of 'all signals', he theoretically encompasses: PageRank and link juice, accumulated domain authority, indexing history, user signals (CTR, session times observed via Chrome or Search Console), performance data (Core Web Vitals), and any potential penalties or manual actions.

The transfer does not happen instantly. Google needs to recrawl the old domain, discover the redirects, explore the new domain, and then gradually consolidate the signals. This process may take anywhere from a few days to several weeks, depending on the site's size and crawling frequency.

Why does Google insist that 'it works very well'?

Because for years, domain migrations were seen as high-risk operations, often followed by sharp drops in traffic. Google seeks to reassure: well-executed migrations are no longer a lottery. The algorithm has evolved to handle these transitions more robustly.

Let’s be honest: this statement remains cautious with the word 'typically'. Google does not guarantee a 100% transfer 100% of the time — it states that in most cases, it works. This leaves the door open for exceptions that are regularly observed in practice.

• One-to-one migration: each old URL has a direct match on the new domain, with no structural change.
• Transferred signals: link authority, PageRank, indexing history, user signals, technical performance.
• Gradual process: the transfer is not instant; Google must recrawl, discover redirects, and consolidate data.
• 'Typically' means conditions must be met for the transfer to be complete — it is not automatic.

Is this statement consistent with field observations?

Yes and no. In well-executed simple migrations — clean 301 redirects, identical structure, no parallel redesign — a fast and nearly complete transfer is indeed observed. Some sites regain their visibility levels within 2-3 weeks.

However, in complex migrations (CMS change, site mergers, restructuring of hierarchy), even with correct redirects, we see temporary, or even permanent, position losses. Google may struggle to consolidate scattered signals or interpret cascading redirects. [To be verified]: Google has never published quantitative data on the actual success rate of migrations or the share of signals effectively transferred on average.

What nuances should be added to this statement?

The word 'typically' is crucial. It implies that conditions must be met: permanent 301 redirects (not 302), no chains of redirects, a clean new domain (no pre-existing penalty), optimal crawlability of the new site, and up-to-date XML sitemaps submitted promptly.

If any of these conditions are not met, the transfer may be partial or delayed. And this is where it gets tricky: many migrations fail not because Google does not transfer signals, but because the technical conditions are not met. We often see sites with chained redirects, 404 errors on key pages, or crawls blocked by configuration errors.

In what cases does this rule not fully apply?

When the migration is accompanied by a deep redesign (change in URL structure, removal of sections, merging with another site), Google can no longer follow the one-to-one principle. Signals must be reinterpreted in a new context, which slows or dilutes the transfer.

Another problematic case is international migrations with a change of ccTLD (.fr to .com) or hreflang structure. Google must recalculate localized signals, which can lead to visibility fluctuations across markets.

What concrete steps should be taken to ensure a complete signal transfer?

Start by auditing the old domain: comprehensive list of indexed URLs (via Search Console or a Screaming Frog crawl), identifying strategic pages (high traffic, quality backlinks), and checking for the absence of penalties or manual actions in Search Console.

Next, prepare a rigorous redirect mapping: each URL from the old domain must point to its exact equivalent on the new domain via a 301 redirect. Avoid chained redirects (old > intermediate > new) that dilute PageRank and slow down crawling. Test redirects in bulk before the big day with a tool like Redirect Mapper or Screaming Frog.

What mistakes should absolutely be avoided during a domain migration?

Never redirect all URLs from the old domain to the homepage of the new one — it’s a disguised soft 404 that will cause a significant loss of signals. Google will interpret these redirects as missing pages, not as a content transfer.

Also avoid blocking the crawl of the old domain too soon. Keep redirects active for at least 6 months, ideally 1 year. Google needs time to recrawl all URLs, especially deeper pages that are rarely visited. If you disable the old domain after 1 month, Google will not have had the time to consolidate all signals.

How can you check that the signal transfer is going well?

Monitor Search Console daily: number of indexed URLs on the new domain (should gradually increase), crawl errors (404, broken redirects, timeouts), impressions and clicks (should return to pre-migration levels within 2-4 weeks). Compare organic traffic curves before/after with Google Analytics, segmented by strategic page.

Also use position tracking tools (SEMrush, Ahrefs, Ranks) to monitor priority keywords. A lasting drop (more than 3-4 weeks) on strategic queries is a warning sign: investigate redirects, check crawlability, or detect potential technical errors on the new site.

• Establish a comprehensive mapping of 301 redirects (one-to-one, no chains)
• Test all redirects in bulk before the new domain goes live
• Submit new XML sitemaps in Search Console as soon as the migration occurs
• Declare the address change in Search Console (old domain verified)
• Monitor crawl errors, indexing, and organic traffic daily for 4 weeks
• Keep redirects active for a minimum of 6-12 months