Website Migration SEO: How to Redesign, Replatform or Move Domains Without Losing Your Rankings

What counts as a website migration

A migration is any change big enough that search engines have to relearn your site. Some are obvious, like a new domain. Others look harmless, like a redesign on the same platform, until the new templates quietly change every URL.

The common types, from lowest to highest search risk:

Most real projects stack these: a new design on a new platform with new URLs. Treat a stacked migration as the riskiest type in the stack, and plan accordingly.

Why website migration SEO goes wrong

Migrations rarely lose traffic because Google penalizes change. They lose it because something that earned rankings did not survive the move. In our experience the causes are almost always on this list:

1. Missing redirects. Old URLs return 404, and the links and history behind them are lost.
2. Redirects to the wrong place. Everything sent to the home page instead of the matching new page.
3. Content removed in the redesign. The paragraphs that answered the search were cut for a cleaner look.
4. Staging settings shipped to production. A noindex tag or a robots.txt block left on at launch.
5. Internal links broken or thinned out. New navigation drops pages that used to be one click from home.
6. Tracking not migrated. Not a ranking loss, but you lose the ability to see what happened.

Every step in this guide exists to prevent one of those six. Website migration SEO is mostly disciplined bookkeeping.

What Google says about website migration SEO

Google's guidance on site moves with URL changes is the closest thing to an official playbook. The points we hold every project to:

• Map old URLs to new ones. Build the list from sitemaps, analytics, server logs and the CMS, including images, videos, CSS and JavaScript files.
• Use server-side permanent redirects. 301 or 308 where possible. Client-side redirects are a last resort.
• Avoid chains. Redirect straight to the final URL. If a chain can't be avoided, keep it short, ideally no more than 3 hops.
• Keep redirects for at least a year, and longer if possible.
• Update canonicals, hreflang and internal links to point to the new URLs, not through redirects.
• Submit a new sitemap with the new URLs.

On timing, Google says a medium-sized site may take "a few weeks or more" before the new URLs are shown, and larger sites longer, and that visibility may fluctuate temporarily during the move. Small and medium sites should generally move all at once; very large sites can move in sections.

Google's guide to redirects adds why the redirect type matters: with a permanent redirect, "the indexing pipeline uses the redirect as a signal that the redirect target should be canonical." JavaScript redirects should be a last resort because rendering "may fail for various reasons."

Step 1: Benchmark and crawl the old site

Before anyone designs a page, capture exactly what the current site has and what it earns. You cannot protect what you haven't measured, and once the old site is gone you can't go back and look.

• Full crawl of the old site: every URL, status code, title, H1, canonical and word count. Save the file.
• Search Console exports: top pages and queries for the last 12 months.
• Analytics: landing pages that produce organic sessions, calls, forms and sales.
• Backlinks: the pages other sites link to most.
• Rank snapshot: positions for your 50 to 100 most important searches.
• Structured data and tracking inventory: what markup each template outputs and what tags fire where.

Then tag each old URL as one of three: keep (moves with the same or better content), merge (folds into another page) or retire (no traffic, no links, no purpose). That tag drives the redirect map.

Step 2: Build the redirect map

The redirect map is a spreadsheet with one row per old URL and the single best new URL for it. It is the most important document in website migration SEO, and it is where most projects cut corners.

A worked example

Rules for the map

1. One to one wherever possible. Each old page goes to the new page that answers the same question.
2. Never redirect everything to the home page. Google's site move guide warns that sending many old URLs to one irrelevant destination, such as the home page, can confuse users and might be treated as a soft 404.
3. Redirect retired pages with links to the closest relevant page, usually the parent service or category.
4. Update old redirects too. If the old site already redirected A to B, and B now moves to C, point A straight at C.
5. Include file URLs: PDFs and images that earn traffic or links.

Step 3: Carry over what earned the rankings

A redirect passes signals to the new page, but the new page still has to deserve the ranking. Compare every keep page old against new before launch.

Run your top 20 pages through our on-page SEO checklist on staging. If a new page scores lower than the old one, fix it before launch, not after. For markup, our guide to schema markup for SEO covers which types are worth carrying over.

Step 4: Test on staging

Staging is where website migration SEO problems are cheapest to catch. Keep staging out of Google with password protection rather than relying only on noindex, so there is no chance of it being indexed.

• Crawl staging against the redirect map. Every old URL should return one 301 or 308 to the right new URL. No chains, no 404s.
• Crawl staging as a new site. Look for broken internal links, orphan pages and duplicate titles.
• Check rendering. Important content and links appear in the HTML, not only after scripts run.
• Check speed on key templates against Core Web Vitals targets. Our Core Web Vitals guide lists them.
• Test tracking. Submit every form, click every phone link, and confirm each one records in analytics and your CRM.

Then freeze. In the final week, no new pages, no URL changes and no content edits on the old site. Every change after the freeze has to be added to the map by hand, and that is where mistakes come from.

Step 5: Launch day checklist

Launch early in the week, early in the day, with the developer and the SEO lead both available. Then run this list in order.

1. Remove the staging noindex and password; confirm production pages return 200 and are indexable.
2. Check robots.txt on production allows crawling of everything that should rank.
3. Switch on redirects and spot-check the top 50 old URLs by hand.
4. Crawl the full redirect map; fix any 404 or chain immediately.
5. Confirm canonical tags point at the new URLs, not old ones or staging.
6. Submit the new XML sitemap in Search Console. Keeping the old sitemap briefly can help Google find the redirects; Google says warnings that old sitemap URLs redirect are expected during a move.
7. For a domain change, verify both properties and submit the Change of Address tool in Search Console. Google says it is only for domain or subdomain changes, not for HTTPS, www or path moves, and that it forwards signals for 180 days.
8. Inspect the home page and top 20 URLs with URL Inspection.
9. Test every form, call link and checkout once more on production.
10. Update your Google Business Profile website link and major directory listings if URLs changed.

Step 6: The 90-day watch plan

Watch closely at first, then less often. Most problems show up in the first two weeks, and some only after Google has recrawled the whole site.

Compare by page, not just in total. Total traffic can look flat while one important service page has collapsed and a blog post has grown. Our SEO reporting guide shows how to set up page-level views, and our guide to Google Ads conversion tracking covers the paid side, which breaks just as easily in a migration.

Rollback triggers: decide them before launch

Agree in writing, before launch, what counts as a problem and who fixes it how fast. In the moment, teams argue about whether a drop is normal. A trigger list ends the argument.

A full rollback to the old site is rarely needed if the old crawl, the map and the benchmark exist. Most fixes are hours of work. That is the real value of the preparation.

Website migration SEO mistakes we are called in to fix

1. No crawl of the old site. Once it is gone, nobody knows what URLs existed.
2. Bulk redirects to the home page instead of a page-by-page map.
3. Removing redirects after a few months to clean up the server. Google says keep them at least a year.
4. Launching on a Friday with nobody watching over the weekend.
5. Redesigning content and URLs at the same time without a content comparison, so it's impossible to tell which change caused a drop.
6. Forgetting non-HTML files such as PDFs and images that had their own traffic and links.
7. Leaving internal links pointing at old URLs, so every click and crawl goes through a redirect.

The fix for most of them is the same: treat website migration SEO as part of the build, not a task after it. Our technical SEO checklist is a good post-launch health check, and if you sell online, our ecommerce SEO playbook covers how product and category URLs should be handled in a replatform.

How Unified runs migrations

Our web development team and our technical SEO team plan migrations together from the first meeting, so the redirect map and the content comparison are part of the build, not a scramble at the end. We hand-code our sites, which means we control every URL and redirect rule; our article on why we hand-code explains the approach.

For Center for Spiritual Living, the rebuild included migrating 732 events to a custom AI-assisted events platform across a 753-page site, and the organization is #1 on Google and Maps in Fort Lauderdale. Since 2006 we have worked with more than 1,100 businesses, and the rule has held every time: the preparation decides the outcome. Planning a redesign or a move? Talk to us before the design starts, or read about our web design process.

Website migration SEO questions, answered