Website migration and SEO migration: changing your site without losing search traffic

What counts as a website migration

In SEO terms, a migration is any significant change that forces search engines to relearn your website. Moving to a new domain is the obvious example, but far from the only one:

• a new website with a different structure or different URLs;
• replatforming, such as moving from WordPress to a headless CMS or from Magento to Shopify;
• a new domain after a rebrand, merger or acquisition;
• combining several websites, or a whole digital estate, into one;
• adding languages or countries to an existing site;
• switching from http to https, or changing hosting and server configuration.

In every case the underlying issue is the same. Google has indexed your existing pages, assessed them and connected them to searches. If those pages disappear or change without Google being told where they went, much of that accumulated value is lost.

Types of migration and their risk

Risk grows with the number of things that change at once. The more you change in one go, the harder it is to identify the cause if traffic falls. Where possible, avoid combining a domain change, a new platform and a new structure in a single launch.

Why sites lose rankings after a migration

A post-launch drop nearly always has a traceable cause. The usual suspects:

• Missing or careless redirects. Old URLs return errors or all point to the home page.
• Lost content. Pages that ranked were shortened, merged or dropped because they did not suit the new design.
• A leftover block. A noindex tag or restrictive robots.txt from the staging site goes live.
• Weaker internal linking. Important pages end up buried or disappear from the navigation.
• Changed titles and headings. Pages stop being about the searches they used to win.
• Slower templates. A new design with heavy scripts and oversized images.
• Missing structured data, so rich results disappear.
• JavaScript rendering on a new framework that hides content from crawlers.

The encouraging part is that every one of these can be checked before launch.

Before the migration: inventory and benchmark

The most important phase happens before anything changes. Its job is to record what exists and what it is worth.

• A complete URL list, combining a crawl of the current site, the XML sitemaps, Search Console and analytics. This finds old pages that are no longer in the menu but still attract visits or links.
• Value per URL: clicks from search, the queries behind them, conversions and external links.
• A benchmark of rankings, clicks, impressions and enquiries over a representative period, so the post-launch comparison is fair. Allow for seasonality.
• Content that must survive. Pages that perform keep their substance, headings and titles, even if the design changes completely.
• A protected staging site. Restrict the test environment with a password rather than relying on robots.txt alone, so it never ends up in the index.

A pre-migration SEO audit also reveals problems you would rather not carry over, such as duplicate pages or a muddled structure.

The redirect map: every old URL gets a destination

The redirect map is the core of an SEO migration. It pairs every valuable old URL with the most relevant new URL, using a permanent 301 redirect. Google explains how redirects pass signals in its documentation on redirects and Google Search.

Rules for a sound redirect map

• Keep URLs unchanged where you can. The safest redirect is the one you never need.
• Redirect page to page. An old service page goes to its new service page, not to the home page.
• No chains. Point straight at the final destination, and update redirects left over from earlier migrations.
• Remove deliberately. A page with no successor and no value can return a 404 or 410. A page with links or traffic deserves a fitting destination.
• Update internal links so your navigation and copy point directly at the new URLs rather than through redirects.
• Test the map on staging by crawling the full list of old URLs and checking every response.

Replatforming: parity before improvement

Moving to a new CMS or ecommerce platform is where most avoidable losses happen, because the new system makes different default choices. Check template by template that the new platform reproduces what mattered on the old one:

• titles, meta descriptions and headings carried across or deliberately improved;
• canonical tags, hreflang and structured data output correctly;
• category and product content, filters and pagination handled in a way search engines can follow;
• internal links and breadcrumbs at least as strong as before;
• rendered HTML that contains the content, not an empty shell waiting for JavaScript.

Shopify, for example, imposes fixed URL prefixes, so almost every URL changes when you move to it; our Shopify SEO page covers the specifics. The detail of crawling, rendering and indexing is set out under technical SEO.

Changing domain or merging sites

A new domain after a rebrand, merger or acquisition carries the highest risk, because every address changes at once. Beyond the redirect map, register the new domain in Search Console, verify both properties and use the Change of Address tool to tell Google about the move. Ask the most valuable sites that link to you to update their links, and update your own profiles, Google Business Profile and directory listings.

When merging sites, decide topic by topic which page becomes the definitive one, combine the best content into it and redirect the others. Simply redirecting a whole domain to the new home page throws away most of its value. Companies consolidating several country domains should also review their structure under international SEO before choosing the target set-up.

Launch day and the weeks after

On launch day we work through a fixed checklist before anyone else looks at the site:

1. The new site is indexable: no staging noindex, a correct robots.txt.
2. Redirects work for a large sample, including every high-value URL.
3. The new XML sitemap is live and submitted in Search Console.
4. Canonicals, hreflang and structured data reference the new URLs.
5. Forms, phone links, consent and conversion tracking work.
6. For a domain change, the Change of Address request has been submitted.

Then the monitoring starts. Google's guidance on site moves with URL changes notes that rankings can fluctuate while the new site is processed and advises keeping redirects in place for a long time, at least a year. We track indexing, crawl errors, 404s and key queries against the benchmark, and fix problems while they are still small.

What is realistic, and how we run a migration

Nobody can promise that nothing will move. After a domain change or a new structure, Google needs time to reprocess the site, and a temporary dip is part of that. How long depends on the size of the site and how often Google crawls it. What can be done is to sharply reduce the risk of lasting loss, find problems quickly, and use the migration to improve the site: a clearer structure, faster pages and better content often leave you stronger than before.

If we build your new website, the migration is part of the project; see website redesign. If another agency builds it, we can lead the SEO side alongside them, in the role described on our SEO consultant page. The effort depends on the number of URLs, the type of migration, the platforms involved and how many markets are affected.

Every engagement starts with the paid Beacon Strategy Session: 50 minutes with the founder for £225 excluding VAT. It is a conversation about your plans and whether we fit, not a migration review. Afterwards we decide whether to take the project on; if we do, a proposal with fixed scope and fixed price follows.