SEO website migration: the guide to preserving your rankings

Website SEO migration: the guide to protecting your search rankings

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A website migration is often a necessary step in a site's lifecycle: changing CMS, redesigning the interface, updating the site architecture, changing domain names, moving to new hosting, or making significant changes to the URL structure.‍

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However, a poorly planned migration can also impact your organic search performanceInaccessible pages, forgotten redirects, deleted content, indexing errors or changes to internal linking can lead to a loss of visibility on Google.‍

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The goal of an SEO migration is precisely to avoid these issues. It involves anticipating the impacts of the change, preserving existing SEO signals as much as possible, and quickly monitoring for any anomalies after launch.‍

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To successfully execute an SEO website migration, you must think in terms of three phases : before, during, and after the migration.

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What is an SEO website migration?

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An SEO migration refers to all the operations carried out to preserve crawling, indexing, and organic performance of a site during a major technical or structural change.

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Not all changes made to a site necessarily require a full migration plan. Changing a color or adding a new section to an existing page generally presents little risk.

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The situation is different as soon as it concerns how search engines discover, understand, or index pages.

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What changes require an SEO migration?

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An SEO migration should be considered in cases such as:

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• changing your domain name;
• changing your hosting provider;
• switching from HTTP to HTTPS;
• changing your CMS;
• migrating from WordPress to Webflow, for example;
• significant changes to your site structure;
• mass URL changes;
• merging multiple sites;
• redesign resulting in the deletion or consolidation of pages.

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A migration can also combine several of these changes. A complete redesign can therefore simultaneously involve a CMS switch, a new architecture and the modification of hundreds of URLs.

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The larger the migration scope , the more rigorous the SEO preparation must be.

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‍Why can a website migration affect SEO?

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Google associates various signals with each URL: page content, internal links, backlinks, age, popularity, and relevance to specific search queries.

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When a URL disappears without a redirect, some of these signals may be lost. Google must also discover the new pages, understand their relationship to the old ones, and gradually re-evaluate the new site structure.

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The main risks include:

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• pages that suddenly return a 404 error;
• incorrect redirects;
• important pages that are no longer indexable;
• content deleted during the redesign;
• significant changes to internal linking;
• backlinks that still point to old URLs;
• canonicalization errors;
• crawl issues.

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A slight fluctuation in traffic or rankings may occur after a major migration. The goal is therefore not necessarily to prevent any variation, but to limit avoidable losses and allow search engines to quickly understand the new version of the site.

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How to prepare for an SEO website migration?

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The success of a migration is largely determined before going live. Migrating without a precise understanding of the performance and structure of the existing site is like making the change without a real point of comparison.

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Conduct a comprehensive SEO audit of the existing site

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The first step involves conducting a site assessment before any changes are made.‍

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The audit should specifically help toidentify :

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• currently accessible URLs;
• indexable pages;
• pages generating the most SEO traffic;
• pages ranking for strategic queries;
• title tags and meta descriptions;
• key content;
• internal linking;
• backlinks;
• any technical errors;
• site performance;
• conversions generated by organic traffic.

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It is particularly important toidentify the pages that are already generating traffic or conversions. These URLs must be among the most closely monitored elements during the migration.

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This audit also allows you to establish a benchmark before the migration. Data from Google Search Console, GA4 , or a rank tracking tool can then be compared with the data observed after the site goes live.

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Without a baseline, it becomes much more difficult to determine if a drop in traffic is actually caused by the migration.

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Back up the site and prepare the staging environment

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Before any technical migration, a full backup must be performed.

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Depending on the environment used, this may include:

• site files;
• the database;
• content;
• images and other media;
• technical settings;
• specific CMS configurations.

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The new site should ideally be tested in a staging environment before it goes live.

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This pre-production phase allows you to verify the functionality of the pages, content, responsiveness, forms, internal linking, and key SEO configurations before making the new site accessible to users and search engines.

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However, you must ensure that this test environment is not indexed by Google.

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Mapping old and new URLs

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The URL mapping is one of the most important steps of an SEO migration. The goal is simple: identify what happens to every important old URL after the migration.

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When a page keeps the exact same URL, no redirection is necessary.‍When the address changes, a 301 redirect should generally be set up to the most relevant new page .‍

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Finally, when content is deleted, you must determine if there is actually another relevant page to redirect the user to. Automatically redirecting all old pages to the homepage is generally not a best practice.‍

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The mapping must be prepared before going live so that redirects can be activated as soon as the switch occurs.

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SEO website migration: what actions should be taken during launch?

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The day of the migration is the most critical phase of the project. The goal is to make the new site accessible while minimizing disruptions for users as well as for search engines.

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Set up 301 redirects

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301 redirects are used to indicate that an old URL has been permanently moved to a new address. When a page URL changes, the redirect should point to the page that best matches its original content.‍

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For example: /agence-seo-paris/ → /seo/agence-seo-paris/ This matching logic is preferable to a blanket redirect to the homepage.‍

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Once the redirects are deployed, they must be tested to ensure they are working correctly and not creating any redirect chains or loops .

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Control crawling, indexing, and SEO tags

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Some seemingly simple errors can have significant consequences after a migration.

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In particular, you must check:

• the robots.txt file;
• noindex directives;
• canonical tags;
• the XML sitemap;
• HTTP status codes;
• title tags;
• meta descriptions;
• internal links;
• any hreflang tags.

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A common mistake is, for example, to keep a directive used to prevent the site from being indexed while in staging.‍

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The new site may then work perfectly for users while remaining invisible to Google.‍

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The XML sitemap must also reflect the new structure of the site and primarily contain indexable URLs returning a 200 HTTP code.

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Verify hosting, DNS, HTTPS, and site functionality

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When the migration includes a change of host, several technical elements must be carefully checked. The new environment must be verified in particular before updating the DNS.

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You must check:

• the presence of the files;
• the database connection;
• the SSL certificate;
• the HTTPS version of the URLs;
• the functionality of the forms;
• the mobile display;
• the loading times;
• the analytics scripts;
• the general availability of the site.

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Whenever possible, theold environment should remain accessible until the new one is fully operational. The DNS update can then allow the domain name to point to the new hosting.

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How do you check SEO after a website migration?

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The launch does not mark the end of an SEO migration. The first few days following deployment are, on the contrary, crucial for quickly identifying any potential issues.

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Check for technical errors immediately after launch

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A full site crawl must be performed after the migration.

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It is particularly useful for identifying:

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• 404 errors;
• old URLs that were not redirected;
• redirects to the wrong pages;
• redirect chains;
• redirect loops;
• broken internal links;
• important pages set to noindex;
• canonicalization errors;
• pages that have become inaccessible.

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It is also useful to compare this crawl with the one performed before the migration.‍

A significant and unexplained drop in number of pages, for example, can reveal a structural or accessibility issue.

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Monitor Google Search Console and indexing

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Google Search Console becomes particularly important after a migration.

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It allows you to track how Google gradually discovers and processes the new version of the site.

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You should specifically monitor:

• the indexing of new URLs;
• the gradual disappearance of old pages;
• crawl errors;
• any potential sitemap issues;
• trends in clicks and impressions;
• the performance of strategic pages.

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An old URL may continue to appear for some time in the search results. Google must gradually crawl the redirects and integrate the new structure.‍

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The goal is therefore more aboutobserving the general trend than seeking the immediate disappearance of all old URLs.

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Compare traffic and SEO performance before/after

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The post-migration performance must then be compared with the benchmark established before the launch. Above all, you must analyze the variations page by page rather than just looking at the overall traffic.‍

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A sharp drop concentrated on a few key pages can indicate a redirection, indexing, or content issue that is much easier to identify.

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SEO website migration: mistakes to avoid

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Several errors occur regularly during website migrations.‍
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• Migrating without a prior audit it is then impossible to know precisely what needs to be kept and to compare performance before and after.
• Changing URLs without preparing redirects: the old pages become inaccessible and search engines have to start over with completely new URLs.
• Forgetting certain traffic-generating pages : not all pages have the same SEO importance. Strategic URLs must be identified before launch.
• Deleting content without analyzing its performance: a page deemed secondary from a commercial standpoint may still generate traffic or benefit from valuable backlinks.
• Leaving the staging environment indexable : Google may discover duplicate versions of the site or index staging URLs.
• Keeping a noindex tag after going live: this error can prevent entire sections of the new site from being indexed.
• Breaking the internal linking structure : internal links should point directly to the new URLs rather than relying solely on redirects.
• Forgetting backlinks : when a URL with external links changes, its redirect requires special attention.
• Not test the site on mobile: a migration must preserve both SEO and user experience.
• Do not monitor Search Console : some anomalies only appear after Google's bots have crawled the site.‍
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An effective SEO migration relies less on a single technical operation than on a series of checks before and after the change.

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SEO website migration checklist

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Here are the main checks to include in your migration plan.

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Before migration

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Preparation must bring together both the SEO, design, and development.‍

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In particular, you need a full crawl of the old site, a performance benchmark, a backup, a URL mapping and a staging environment advanced enough to carry out the key checks.

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On the day of the migration

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The deployment must be accompanied by an immediate audit of strategic pages.

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The 301 redirects, canonical tags, indexing directives, the XML sitemap, HTTPS, and analytics tracking must be checked without delay.

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Post-migration

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Once the new site is live, enhanced monitoring must be maintained. Any detected errors must be fixed promptly, especially those affecting pages that previously generated traffic, conversions, or backlinks.‍

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At Afalence, we integrate these SEO challenges right from the design phase of redesign and migration projects. The goal is to evolve the site without starting from scratch in terms of search engine optimization, particularly during migrations to Webflow or redesigns involving a new architecture.

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FAQ on SEO website migration

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Does a site migration cause a loss in SEO rankings?

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Not necessarily. A migration can cause temporary fluctuations while Google discovers the new URLs and processes the changes made to the site.

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A well-prepared migration aims to preserve content, important URLs, internal linking, and key SEO signals in order to limit avoidable losses. Conversely, a migration without a plan for redirects or technical oversight can cause a significant drop in visibility.

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How do you change your domain name without losing your SEO?

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A domain change must be prepared URL by URL.The old pages must be mapped to their equivalents on the new domain, then redirected using 301 redirects.

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You must also preserve strategic content, update internal links, check the sitemap, and closely monitor indexing after the migration.

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Should you conduct an SEO audit before a migration?

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Yes.

TheAn audit helps understand the existing site structure andidentify the pages, content, and performance metrics that must be preserved. It also serves as a baseline to compare results after the migration.

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Without this audit, it becomes more difficult to pinpoint the source of any potential drop in traffic.

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How long should you monitor SEO after a migration?

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The monitoring must be significantly intensified after launch and continue until crawling, indexing, and key SEO metrics stabilize. The duration depends in particular on the size of the site, the scale of the migration, and the frequency with which Google crawls its pages.

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The important thing is not to consider the migration finished as soon as the new site is live. Post-migration monitoring is an integral part of the SEO project.