Google's New Warning on Partial Site Moves Could Upend Your Migration Plan

Key Takeaways

For marketers planning domain changes or rebrands, the main implications are:

• Treat staggered migrations as higher risk. Google will not view a partial move (for example, only the homepage and content hub) as a true site move, which can prolong ranking volatility and split authority between domains. So what: if you must phase the move, shorten the overlap window and group pages into clear, self-contained waves.
• Google Search Console's Change of Address tool is a supporting signal, not a cure-all. Using it while many high-traffic URLs remain on the old domain creates a mismatch between what the tool claims and what crawlers see. So what: trigger Change of Address only when the bulk of your core URLs and internal links already point to the new domain or will do so within a short period.
• Expect messy data and tracking during a partial move. Search Console, analytics, and server logs will fragment across two domains, making it harder to separate normal migration noise from genuine performance problems. So what: build a URL-level migration map, define KPIs per phase, and set finance and leadership expectations around a wider error range in traffic and revenue forecasts.
• Brand and paid media effects spill over from SEO. With two domains visible in search and ads, users may be unsure which site is "official", and ad approvals or Quality Score can be affected by inconsistent landing domains. So what: bring brand messaging and ad URLs into line quickly so the new domain becomes the default destination across all channels.

Situation Snapshot

This analysis is prompted by a Search Engine Journal report on a Bluesky thread where a site owner asked John Mueller about using Google Search Console's Change of Address tool during a phased move between domains.

Key facts:

• The questioner initially framed the situation as a full site move and asked if they could submit a Change of Address while "a few old URLs" still received traffic and lacked redirects. Mueller replied that this is "generally fine", noting that the tool mainly checks the homepage redirect and that some moves keep the old robots.txt file open to allow crawling.
• After the person clarified that the homepage had moved but many product and category pages would remain on the old domain for now, Mueller revised his answer. He said Google would not see this as a full site move, that using Change of Address would create "a messy situation" until everything was migrated, and that tracking performance would be harder while Google tried to interpret two partly overlapping sites.
• Mueller again referenced Google's "understanding" of a site - a phrase he has also used in discussions about sitewide quality assessment and how a site fits into the wider web.
• Search Engine Journal connected these comments to prior guidance: avoid combining site moves with other major changes, and expect months-long timeframes for Google to fully reassess a site after large structural changes.

Breakdown & Mechanics

At a systems level, this is about how Google transfers signals from one host to another, and what happens when those signals conflict.

1. How a clean site move normally works

In a complete move, the signals line up cleanly:

• Old URLs consistently 301 redirect to new equivalents.
• Internal links on the old site gradually shift to the new domain or are removed as the old site winds down.
• Canonical tags, sitemaps, and hreflang (if present) all confirm that the new URLs are the primary versions.
• The Change of Address tool is used once the old domain largely behaves like a shell pointing to the new one.

In that situation, Google's internal view looks something like:

Old URL set A → 301 to new URL set B → consistent signals → transfer of ranking signals and consolidation of "site understanding" to the new host.

2. What breaks in a staggered, partial move

With a staggered migration where the homepage and some sections move but many high-value pages stay on the old domain, Google sees mixed signals:

• Some old URLs 301 to the new domain.
• Other old URLs remain live and continue earning impressions, clicks, and links.
• The homepage - the main anchor of site identity - moves, but service or product pages that drive revenue sit on the old host.
• The Change of Address tool may claim "domain A moved to domain B" while crawlers still find substantial sections operating normally on domain A.

Internally, that looks more like:

Old URL set A1-A1000 → some 301 to B1-B200, others stay on A → Change of Address hint says "A → B" → Google must override its own hint for many pages.

Result: Google splits signals, needs to maintain two parallel "site models" (old and new), and will be conservative in fully transferring trust and rankings.

3. Google's "site understanding" and why domain-level clarity matters

Mueller has repeatedly hinted that Google builds an aggregate understanding of a site: what topics it covers, how it performs for users, what quality level it maintains, and where it fits relative to other sites in its space. That understanding is strongly tied to the host or domain.

When the homepage and some sections move but others stay:

• Brand and navigational intent may start mapping to the new domain (because the homepage moved).
• Informational or transactional intent may still map to the old domain (because the bulk of ranking URLs sit there).
• Quality and trust signals need to be re-scored for the new site, but the content base is incomplete, so Google's model of the new domain can look thin or unstable at first.

This creates a feedback loop:

Partial move → fragmented internal linking and redirects → split site understanding → conservative signal transfer → prolonged volatility until the structure stabilizes.

4. The role and limits of the Change of Address tool

The Change of Address tool in Search Console is a strong hint, not a command. It is designed for scenarios where:

• OldDomain.com → NewDomain.com is broadly true for the whole site, and
• Most key sections are in place on the new domain when the change is submitted.

In a partial move, the tool:

• Still requires the homepage redirect to succeed.
• Signals to Google that traffic and signals for OldDomain.com should, in general, shift to NewDomain.com.
• Must be overridden on a URL-by-URL basis when crawlers see that many old URLs have not moved.

Mueller's "messy situation" comment reflects this conflict: the domain-level hint from Change of Address fights with URL-level reality, so Google delays full consolidation until your structure and redirects match what the tool claims.

Impact Assessment

From a marketing standpoint, this reframes staggered migrations as a trade-off: operational convenience versus greater SEO and analytics risk.

Organic search and content

• Direction: Negative risk if the partial phase is long; closer to neutral if overlap is short and phases are well-bounded.
• Effects:
  • Authority and relevance signals are split between old and new domains, especially if external links and internal navigation now point in mixed directions.
  • Brand queries may start to favor the new domain while long-tail or product queries still favor the old, scattering your funnel across two properties.
  • Search Console reporting becomes fragmented; aggregate trends can hide section-level winners and losers.
• Actions:
  • Plan migrations by coherent sections (for example, move all category and product URLs in a single wave) rather than by isolated templates.
  • Keep duplicate or near-duplicate content (old versus new versions) live for as short a window as practical.
  • Use detailed redirect maps and index coverage checks to validate that sections are genuinely complete before moving on.

As a simple, hypothetical model: if 60% of your organic revenue comes from pages that remain on the old domain for three months, but internal links and marketing campaigns begin favoring the new domain, it is reasonable to expect some temporary drag on revenue while users and signals are pulled in two directions. The exact size of that impact will vary by site; this example is for illustration, not a forecast.

Paid media and brand

• Direction: Mixed, but exposure to confusion increases while two domains are active.
• Effects:
  • Brand search ads and organic sitelinks may show different domains, which can weaken perceived trust and lower click-through rates on the new brand.
  • Ad approval and Quality Score can be affected if ad copy references a brand tied to the new domain but landing pages still reside on the old one, or if tracking templates alternate between domains.
  • Remarketing, Performance Max, and social campaigns may need manual adjustments to domain rules, increasing operational overhead.
• Actions:
  • Decide early which domain will be the single source for paid landing pages for each campaign type and stick to it.
  • Refresh ad copy and extensions so they consistently reference the target domain during each phase.
  • Coordinate migration timing with brand campaigns; avoid launching a major awareness push while the organic experience is split across two domains.

Analytics, reporting, and operations

• Direction: Higher complexity and noise during the partial period; risk of misreading performance.
• Effects:
  • Data splits across multiple Search Console properties and analytics streams; standard dashboards are likely to under-report or duplicate traffic.
  • Revenue attribution can skew if conversion tracking is not adjusted for cross-domain flows or if default channel groupings change when domains change.
  • Internal teams (SEO, paid, product, finance) may each look at different slices and reach conflicting conclusions.
• Actions:
  • Maintain a central migration log with dates, sections moved, and redirect batches; link this log to performance reports.
  • Define migration-specific KPIs (for example, share of migrated URLs indexed, share of traffic landing on the new domain for brand queries) alongside business KPIs.
  • Treat the partial migration window as a special reporting period with clear caveats for executives and investors.

Overall, businesses that can compress migrations into decisive, section-based waves are likely to fare better. Those that stretch moves over many months due to platform limitations or organizational delay carry a higher risk of prolonged organic underperformance and murky reporting.

Scenarios & Probabilities

The following scenarios are forward-looking assessments, not guarantees.

• Base case - short phased move with moderate noise (likely): The homepage and some sections move first, but the remaining high-value sections follow within 4-8 weeks. Change of Address is either delayed until most URLs have moved, or used carefully once redirects are close to complete. Google sees a somewhat messy but finite transition, with noticeable volatility for several weeks and partial recovery over the next few months. Brands that monitor closely and fix gaps quickly see medium-term stabilization.
• Upside case - section-based moves with tight execution (possible): The site is migrated in two or three clearly defined waves (for example, informational, then transactional), each wave executed as a near-total move for that section. Change of Address is timed to when 80-90% of traffic-driving URLs already redirect correctly (this is an assumption for planning, not a published threshold). Clear internal linking and minimal duplication help Google connect the dots faster, leading to smaller and shorter traffic dips than a typical large-scale migration.
• Downside case - extended staggered move and inconsistent signals (edge): The homepage moves early, but major sections stay on the old domain for six months or longer. Some URLs redirect; others do not; content is duplicated between domains. Change of Address is triggered early, but the site's behavior contradicts it. Google becomes conservative in signal transfer, and both domains lose clarity in how they are evaluated. In this case, a business heavily reliant on organic search could see sustained underperformance that persists even after final cleanup, simply because it takes additional time for Google to rebuild a coherent view of the new site from a history of conflicting signals. This scenario is speculative but consistent with Mueller's warnings about added difficulty.

Risks, Unknowns, Limitations

• There is no public threshold for when Google treats a move as "full" versus "partial" at the domain level (for example, percentage of URLs or traffic moved). Any cut-offs used in this analysis are hypothetical.
• Google's internal handling of the Change of Address tool is not fully documented; public comments indicate it is a signal layered on top of URL-level behavior, but not the exact weighting.
• Mueller's comments are qualitative. They indicate added complexity and risk but do not quantify expected traffic loss, recovery curves, or probability of failure.
• The impact of a staggered move will vary widely by site size, link profile, content mix, and how long the partial state persists. The simple models in this analysis are illustrative only.
• Prior case studies of migrations are often anecdotal and confounded by other changes (design, content pruning, platform moves), which makes it hard to isolate the specific effect of staggering alone.
• This analysis would be weakened or overturned if large-scale, well-measured migrations showed no meaningful difference in performance between staggered and complete moves when redirects and content parity were otherwise strong.

Sources

• Search Engine Journal / Roger Montti (2025), article: "Google Explains Why Staggered Site Migrations Impact SEO Outcome."
• John Mueller (2025), Bluesky thread: responses on using Google Search Console's Change of Address tool for partial site moves (quoted and summarized in Search Engine Journal).
• Google Search Central documentation, "Move a site with URL changes" and related guides on using the Change of Address tool.
• Search Engine Journal (2023), article: "Google: Don't Combine Site Moves With Other Big Changes."
• Search Engine Journal (2022), article: "It Takes Months For Google To Evaluate Website Quality Across The Web," summarizing John Mueller's comments on sitewide quality and how sites fit into the overall internet.