You are excited about a new website. A fresh design, a new platform, maybe a better domain name. Then someone warns you: "Be careful, sites lose half their traffic after a redesign." That sounds scary, and sadly it does happen. But it almost always happens for the same few reasons, and those reasons can be planned for.
In this lesson, I will explain what counts as a site migration, why traffic drops after one, how to build a redirect map, when to use Google's Change of Address tool, and what to check before and after launch. By the end, you will have a step-by-step plan you can follow, or hand to your developer, for any move.
What counts as a site migration?
A site migration is any big change to your website that can affect how search engines find, crawl and understand it. Most people think of moving to a new domain, but many other projects count too. Here are the common types:
| Type of move | Example | Do URLs change? | SEO risk |
|---|---|---|---|
| HTTP to HTTPS | http://example.com to https://example.com | Yes (protocol) | Low, if done carefully |
| Domain change | oldbrand.com to newbrand.com | Yes (every URL) | High |
| URL structure change | /index.php?id=12 to /services/plumbing/ | Yes (paths) | Medium to high |
| Platform or CMS change | Wix to WordPress, Shopify to WooCommerce | Often | Medium to high |
| Redesign | New theme, menus and page layouts | Sometimes | Medium (content and links often change) |
| Hosting change | New server, same URLs | No | Low |
| Merging sites | Two blogs combined into one | Yes | High |
Google splits moves into two groups: moves without URL changes, such as a hosting change, and moves with URL changes. The second group needs much more care, and it's the main focus of this lesson. If you are switching to HTTPS, my lesson on HTTPS and site security covers that specific move.
Why do sites lose traffic after a migration?
Your rankings are tied to your URLs. Over time, each URL builds up signals: links from other sites, internal links, history in Google's index. When a URL changes without a proper redirect, those signals are left behind at the old address. It's like moving house without forwarding your mail. Letters keep arriving at the old place, and nobody picks them up.
Here are the usual causes of a post-migration drop:
- Missing redirects: old URLs return 404 errors instead of sending people and Google to the new page.
- Lazy redirects: every old URL is sent to the new homepage instead of the matching page.
- Lost content: pages that ranked well were cut, shortened or merged during the redesign.
- Blocked new site: a
noindextag or a robots.txt block from the test site is left in place at launch. - Broken internal links: menus and content still point to old URLs, creating redirect chains or 404s.
- Changed titles and headings: careful on-page work from earlier, like your title tags, is lost in the new templates.
Some ups and downs are normal even when everything is done right. Google's site move guide says rankings may fluctuate during the move, and that for a medium-sized site it can take a few weeks or more for most pages to move in Google's index. Larger sites take longer. The goal is a short dip, not a lasting loss.
How do you build a redirect map?
A redirect map is a simple spreadsheet with two columns: the old URL and the new URL it should point to. It's the single most important document in any migration. Here is how I would build one:
- Collect every old URL. Use several sources, because each one misses something: your current XML sitemap, a full site crawl, the Pages report in Search Console's Performance section, your analytics landing pages, and the Links report for pages that other sites link to.
- Don't forget files. Google's guide reminds you to include images, videos, PDFs, and JavaScript and CSS files.
- Mark the important URLs. Note which pages bring traffic, conversions or backlinks. These need the most attention.
- Match each old URL to its new home. The best match is the page with the same or very similar content.
- Decide what to do with pages that won't exist anymore. If there's a close replacement, redirect to it. If there's truly nothing relevant, let the old URL return a 404 or 410 instead of forcing it onto the homepage.
- Test the map. Before launch, check that every new URL in the map loads with a 200 status.
Here is a tiny invented example of what the sheet looks like:
| Old URL | New URL | Note |
|---|---|---|
| /services.php?id=3 | /services/boiler-repair/ | Top traffic page |
| /blog/2019/05/boiler-tips | /blog/boiler-maintenance-tips/ | Has backlinks |
| /winter-offer-2021/ | (none, return 410) | Expired offer, no replacement |
| /about.html | /about-us/ |
Which kind of redirect should you use?
Use server-side permanent redirects. Google recommends 301 or 308 redirects where possible, and treats JavaScript or meta refresh redirects as a last resort. Point each old URL straight at its final destination, so you don't create redirect chains (A to B to C). My lesson on redirects explains the different types, and my posts on 301 vs 302 redirects and redirect chains go deeper.
Keep the redirects for a long time. Google's guide says to keep them generally for at least one year, and from a user's point of view, indefinitely, because old links in emails, bookmarks and other sites keep working.
When should you use Google's Change of Address tool?
The Change of Address tool in Search Console tells Google that your whole site has moved from one domain or subdomain to another, for example from oldbrand.com to newbrand.com. It helps Google move its index from the old site to the new one.
It is not for every move. Google's help says it doesn't support:
- Moving from HTTP to HTTPS (Google detects this automatically).
- Switching between www and non-www on the same domain.
- Moving pages to new paths within the same site.
- Changing hosts or CDNs without any visible URL change.
To use it, you must be a verified owner of both the old and new properties in Search Console, and your redirects must already be in place, at least from the old homepage to the new one. Google shows a move notice for 180 days and asks you to keep redirects in place for at least that long, longer if old URLs still get search traffic. Combined with the one-year advice above, I suggest you simply never remove them.
Your pre-launch and post-launch migration checklist
Most migration disasters can be caught with a checklist. Here is the one I would use. Most items come straight from Google's site move guide; a few, like timing, are my own advice.
Before launch
- Benchmark: save a copy of current rankings, top pages, traffic and conversions so you can compare later.
- Crawl the old site and save the full list of URLs, titles and meta descriptions.
- Finish and test the redirect map.
- Check the new site has the same important content, titles and headings, or better.
- Add self-referencing canonical tags on new pages and update hreflang if you have international versions.
- Update internal links to point straight at new URLs.
- Prepare a new XML sitemap with the new URLs.
- Verify the new site in Search Console and set up analytics on it.
- Make sure the new server can handle extra crawling; Google tends to crawl more heavily after a move.
- Plan the launch for a quieter period for your business, not your busiest season.
On launch day and after
- Remove any
noindextags and development robots.txt blocks from the new site. - Switch on the redirects and test a sample of old URLs, especially your top pages.
- Submit the new sitemap in Search Console. Google notes that warnings about redirecting URLs in the old sitemap are normal.
- If you changed domains, submit the Change of Address request.
- Crawl the new site to catch broken links, redirect chains and missing titles.
- Watch the Page indexing report, the Performance report and your 404 errors every few days for the first weeks. My post on fixing 404 errors shows how.
- Ask sites that send you important backlinks to update their links to the new URLs.
For a printable version with even more detail, see my website migration SEO checklist. And if a drop happens to overlap with a Google update, my post on telling a migration problem from an algorithm update will help you work out which is which.
Try it: start a redirect map for your own site
Even if your redesign is months away, starting the redirect map now is the best thing you can do. Spend 20 minutes on this:
- Open a spreadsheet with three columns: Old URL, New URL, Note.
- In Search Console, open Performance, click the Pages tab, set the date range to the last 12 months, and export the list.
- Paste the top 50 pages into the Old URL column.
- In the Note column, mark pages with lots of clicks as "Priority."
- For each priority page, write where its content will live on the new site. If you don't know yet, write "decide," and raise it with your designer.
This short list protects the pages that bring most of your search traffic, and it's often the moment people realize the new design accidentally drops an important page.
Questions beginners ask about site migrations
How long does it take to recover traffic after a migration?
Google says a medium-sized site can take a few weeks or more for most pages to move, and larger sites take longer. If you still see a big drop after a couple of months, check redirects, indexing and lost content.
Can I redirect all old pages to my new homepage?
No. Google advises against sending many old URLs to an irrelevant page such as the homepage. Redirect each page to its closest match, and let truly removed pages return a 404 or 410.
Should I change my design and my domain at the same time?
Doing several big changes at once makes it harder to find the cause of any problem. If you can, separate them. If you can't, follow the checklist even more carefully.
Does a hosting move affect SEO?
If the URLs stay exactly the same, a hosting move is low risk. Make sure the new server is fast and reliable, and keep an eye on server errors in Search Console afterwards.
When can I remove the old redirects?
Google suggests keeping them for at least one year, and the Change of Address tool asks for at least 180 days. Since redirects cost almost nothing to keep, I suggest leaving them in place for good.
Plan the move before you pack the boxes
In brief, a migration is any big change that affects your URLs, content or structure. Traffic drops come from missing or lazy redirects, lost content and leftover blocks from the test site. Build a redirect map from several URL sources, use page-to-page 301 or 308 redirects, use the Change of Address tool only for domain moves, and follow a checklist before and after launch.
In the next lesson, you will learn how to run a basic technical SEO audit, which is also the perfect health check after a migration. If you are planning a move and want an experienced team to manage the SEO side, you are welcome to request a quote from us.