A website migration is the only routine project that can wipe out years of search visibility in a single afternoon. Rebuilds, replatforms, domain changes and even a tidy-up of URL structure all carry the same risk, and the damage rarely announces itself on launch day. It shows up two weeks later as a quiet, steady decline that nobody connects to the release.

The good news is that the causes are well understood and almost entirely preventable. In practice, nearly all migration traffic loss traces back to one thing: an incomplete redirect map. Everything else in this guide is secondary to getting that right.

The one rule: Every URL that currently exists and has any value — traffic, backlinks, or indexed status — must resolve to a single permanent redirect pointing at its closest equivalent on the new site. Not the homepage. Not a chain of three hops. One redirect, to the genuinely equivalent page.

Build the Inventory Before You Build Anything

You cannot redirect URLs you do not know about, and no single source lists them all. Pull from four and merge.

A full crawl of the existing site. This gives you everything reachable by following links, which is the majority but never the whole picture.

Search Console data. Export every URL that has received impressions or clicks. This catches pages that earn traffic but nothing links to internally, which is more common than people expect.

Server access logs. These show what is actually being requested, including old URLs that no longer appear anywhere on the site but still receive traffic from bookmarks, emails and external links.

Your backlink data. Any URL that other sites link to carries value you will lose if it stops resolving. These are the highest-priority redirects in the whole exercise, because the link equity is not recoverable by other means.

Merge those four into one list, deduplicate, and you have the real surface area of your site. On a mature site it will be considerably larger than anyone estimated, and that number alone often changes the project plan.

Mapping Old to New

With the inventory in hand, the mapping is where judgement enters.

Map every URL to its closest equivalent. Where a page has a direct replacement, that is easy. Where content has been consolidated, point to the page that now covers the topic. Where content has genuinely gone and has no successor, allow it to return a 404 or 410 rather than redirecting it somewhere irrelevant.

Resist the temptation to redirect everything to the homepage. Search engines treat a redirect to an unrelated page as a soft 404, so it passes nothing on and produces a poor experience for anyone following an old link. A deliberate 404 on genuinely removed content is a better outcome than a misleading redirect.

Use permanent redirects, and make sure they are single hops. Redirect chains, where the old URL points to a second URL which points to a third, are common after a site has been migrated more than once. Each hop adds latency and dilutes the signal, so always map to the final destination, not to whatever the previous migration left behind.

Watch the details that are easy to miss: trailing slashes, uppercase characters, query-string parameters that produce distinct indexed URLs, and the protocol and subdomain. A migration that fixes the pages but leaves http and www variants unhandled has doubled its problems.

What Else Moves With the Site

Redirects are the biggest risk, but four other things are worth protecting.

Canonical tags and hreflang. After migration, canonicals must point at the new URLs. Stale canonicals pointing to the old domain are a genuinely effective way to prevent the new site being indexed at all. If you run multiple languages, every hreflang cluster has to be updated in step, since a mismatch invalidates the whole set.

Structured data. Any schema on the old pages should carry across, including URLs inside it. It is easy to migrate the visible content and lose the markup, which quietly removes eligibility for rich results.

Metadata. Titles and descriptions should transfer deliberately rather than being regenerated by the new platform’s defaults. A rebuild that replaces well-tuned titles with a template pattern will lose clicks even if rankings hold.

Page speed. A new site is often heavier than the one it replaced. Since Core Web Vitals are assessed on field data collected over a rolling period, a slower site takes weeks to show its full effect, by which time the cause is easy to misattribute. Our guide to Core Web Vitals covers what the thresholds actually require.

Launch and the First 48 Hours

The launch itself is short; the verification is what matters.

Before going live, test the redirect map against the full inventory on a staging environment. Automate it: request every old URL, assert a single 301 and the expected destination. Doing this by hand on a sample will miss the pattern that breaks a thousand URLs.

Confirm the new site is actually crawlable. The most common launch-day disaster is shipping the staging environment’s robots directives or a leftover noindex tag. Check both before anything else.

Submit the new sitemap, and keep the old URLs in a temporary sitemap for a while so crawlers rediscover them and follow the redirects. If the domain changed, use the change of address tool in Search Console.

Then watch the logs rather than the rankings. Crawler activity on the new URLs tells you within hours whether the migration is being picked up. Rankings tell you nothing useful for at least a week.

What Recovery Actually Looks Like

Set expectations before launch, because the shape of the recovery curve causes more panic than the migration itself.

Some fluctuation is normal even when everything is done correctly. Search engines have to recrawl, reprocess and reassociate every URL, and that takes time proportional to the size of the site. A dip of a couple of weeks on a mid-sized site is not evidence of failure.

A well-executed migration typically returns to previous levels within four to eight weeks, sometimes faster on smaller sites. A poorly executed one does not recover on its own, because the cause persists.

The distinction is visible in the data. If Search Console shows a rise in crawl errors and pages dropping out of the index, you have a technical problem to fix. If crawling looks healthy and impressions are simply lagging, you are watching normal reprocessing.

Keep the old site’s analytics and Search Console data exported before launch. Comparing against a baseline you can no longer access is a miserable position, and it happens surprisingly often.

What Website Migration Work Costs

Prices reflect typical UK agency rates and scale with URL count rather than page design.

Redirect mapping and migration QA for a small site of a few hundred URLs generally runs £900 to £2,500. This covers the inventory, the mapping, the automated verification and post-launch checks.

A mid-sized site of a few thousand URLs typically runs £2,500 to £8,000, mostly because the mapping requires more judgement and the verification more tooling.

Large or ecommerce sites with faceted navigation, parameter URLs and international variants start around £8,000 and rise with complexity. Faceted navigation in particular can generate enormous numbers of indexed URLs that need decisions rather than mechanical mapping.

Set against that, the cost of getting it wrong is the revenue from your organic traffic for however long recovery takes, plus the cost of the emergency work to fix it. It is one of the clearer cases for spending money in advance. Our technical SEO audit cost guide covers the related diagnostic work.

Migrate Once, Properly

Mecanik handles migration planning and verification as part of our technical SEO audit and website development services. We build the inventory from all four sources, produce the redirect map, automate verification against it, and monitor crawl behaviour through the first weeks after launch.

We also do this for platform changes specifically, where the URL structure often changes as a side effect of the new system’s conventions rather than by anyone’s decision. Our Drupal migration guide covers one common version of that, and the same discipline applies to any replatform.

If a migration has already happened and traffic has dropped, get in touch with the launch date and we will tell you whether it is a redirect problem, an indexing problem, or normal reprocessing.

Related reading: Technical SEO Audit Checklist for 2026 , Website Redesign UK - When and How in 2026 , Hire a Drupal Developer: Rates, Skills and Vetting and SEO Services UK - What to Expect in 2026 ., How to deal with @font-face

Frequently Asked Questions

Why did my traffic drop after a website migration? Most commonly an incomplete redirect map: URLs that had traffic or backlinks now return errors or point somewhere irrelevant. Other frequent causes are a leftover noindex tag from staging, canonicals still pointing at the old domain, and redirect chains that dilute the signal.

Should I redirect old URLs to the homepage? No. Search engines treat a redirect to an unrelated page as a soft 404, so it passes nothing on and frustrates anyone following an old link. Map each URL to its closest genuine equivalent, and let content with no successor return a 404 or 410 instead.

How long does it take to recover rankings after a migration? A well-executed migration typically returns to previous levels within four to eight weeks, faster on smaller sites. Some fluctuation during recrawling is normal. If crawl errors are rising and pages are dropping out of the index, that is a technical fault rather than normal reprocessing.

What should I inventory before migrating a website? Merge four sources: a full crawl of the existing site, every URL with impressions or clicks in Search Console, server access logs showing what is genuinely requested, and your backlink data. Each catches URLs the others miss, and backlinked URLs are the highest priority to preserve.

How much does website migration SEO work cost? Redirect mapping and verification for a small site of a few hundred URLs typically costs £900 to £2,500. Mid-sized sites of a few thousand URLs run £2,500 to £8,000, while large or ecommerce sites with faceted navigation and international variants start around £8,000.