Google's John Mueller says a domain change of address (Search Console's tool that tells Google a site has moved) can sometimes take far longer than four months to fully process — a point he made while advising a site owner whose completed migration suddenly reverted after four months.

The site owner shared the case on Reddit. They migrated domains at the start of 2026, did the redirects, filed the Change of Address in Search Console and updated internal links right away. Traffic recovered by early April. The new domain reached roughly 5,000 impressions per day.

Then Google flipped it back.

What happened four months after the migration?

More than 5,000 pages on the new domain dropped to "Crawled, currently not indexed" — a Search Console status meaning Google fetched the page but excluded it from the index. The new domain's traffic collapsed to about 20 impressions per week.

At the same time, the old domain reindexed completely. All impressions and clicks began showing again in GSC (Google Search Console) for the old domain. Search results listed the old URLs, and clicks redirected to the new site, counting as ordinary views there.

The owner asked: "Why would Google suddenly revert this four months after everything was fixed? How do I fix this? Do I actually have to fix this since the impressions and clicks are still there, just being redirected?"

What did John Mueller say?

Mueller responded directly on the thread, confirming that long processing times are a known factor. He also offered to inspect the domains if contacted privately.

He said: "Happy to take a look if you want to DM me the domains. Sometimes things just take a particularly long time to be fully processed."

Then he flagged one concrete, confirmed fix:

"One thing which we noticed (and adjusted in the documentation a while back) that can help is to make sure that you have change of address set up in search console for both www and non-www, so that it can fully migrate the domain."

That's a documentation-level correction Google itself made, not speculation — a rare case where a migration failure mode made it into official guidance.

The www/non-www gap matters because canonicalization (Google choosing one URL or domain version to index and rank over the alternatives) can tip back toward the old domain if external links still point at the version Google favors. Treating a broken migration as a canonicalization problem is a reasonable diagnostic frame.

What did the Reddit case leave out?

The report omitted several details that commonly break migrations. These are checklist items from SEO practice, not statements from Google:

• Absolute internal links. Hardcoded URLs like www.example.com/page.html can survive in navigation, footers or contextual content. A full crawl with a tool like Screaming Frog before migration catches them.
• Redirect type. A registrar-level redirect may not preserve URL paths, unlike a URL-to-URL redirect map. HTTPS forwarding can also fail if the old domain lacks an SSL certificate.
• Chained redirects. Multi-hop redirect chains can complicate how Google processes the move.
• Changed navigation structure. Redirects can fail when the new site's navigational structure differs from the old one.
• Stale XML sitemaps. Sitemaps communicate preferred canonical URLs. Google's own documentation advises: "Submitting a sitemap can help make the discovery process quicker, and it's fine to move your site in sections." A sitemap still listing the old domain sends conflicting canonical signals during migration.

Who's at risk and what to watch

The failure pattern hits sites that complete a technically correct-looking move — redirects, Change of Address, recovered traffic — and assume it's finished. A four-month lag before a revert means monitoring can't stop when impressions normalize.

For anyone planning or recovering a migration, the immediate checks are: Change of Address filed for both www and non-www variants, sitemaps rebuilt for the new domain, absolute internal links purged, and redirect chains flattened.

Mueller's confirmation that processing "just takes a particularly long time" in some cases sets the expectation to watch. Monitor both domain properties in Search Console well past the four-month mark, because that's exactly when this site's signals reversed.