Site migration SEO has a reputation for being risky, and the reputation is earned. A domain change, a new CMS or a restructured URL scheme can take months to recover from if it goes wrong. But the risk is concentrated in a few predictable places, and almost all of them are visible before launch. The checklist below follows the five phases set out in Semrush’s migration guide, with the step that causes most damage, URL mapping, given the most attention.
The five phases of a site migration
Semrush’s website migration checklist (Carlos Silva, 5 May 2026) breaks the work into five phases. The order matters: each one depends on the one before it being finished.
| Phase | What it covers |
|---|---|
| 1. Pre-migration planning | Deciding what moves and how, before any build work |
| 2. Build and test | Staging site, technical audit, crawl validation |
| 3. URL mapping | Document URLs, plan redirects and removals, update internal links |
| 4. Completing the migration | Backups, DNS, remove crawl blocks, enable redirects, update external links, Search Console |
| 5. Post-migration monitoring | Watching the site after launch |
Notice how little of that list happens on launch day. Phases one to three are preparation, and they are where migrations are actually won or lost. If you are tempted to compress the timeline, compress phase four, never phase three.
Plan and test before anything moves
Planning starts with a baseline. Before you change anything, crawl the current site and export what you will need to compare later: every indexable URL, titles, canonicals, internal links, and your traffic and indexing figures from Search Console. Without that snapshot, you cannot tell after launch whether a drop is the migration or something else.
The build happens on staging. Crawl the staging site the way you crawled the live one, and compare the two. Missing pages, changed titles, broken internal links and accidental noindex tags all show up here, where fixing them costs nothing. Keep staging blocked from search engines while you work, and write down every block you add, because each one has to come off at launch.
If the migration is part of a wider rebuild, the design decisions bring their own risks. Our post on website redesign SEO covers the content and template changes that tend to cost rankings, separately from the move itself.
Site migration SEO starts with the URL map
The URL map is a spreadsheet with every old URL in one column and its fate in the next. Each row ends in one of two outcomes. Either the content moves, and the old URL gets a 301 redirect to its new home, or the content is removed, and the old URL gets a status code that says so.
- Moved content: 301 redirect to the closest equivalent page. Semrush’s guide notes that 301 redirects preserve authority when content moves. Our guide to 301 vs 302 redirects explains why the permanent version is the one to use.
- Removed content with no equivalent: Semrush advises these “should be set to serve a 410 status code”. Our post on the 404 vs 410 status code covers when each applies.
Two mistakes ruin more maps than any others. The first is redirecting removed pages to the homepage because it is easier than deciding. That is a removal disguised as a redirect, and it sends visitors somewhere they did not ask to go. The second is redirecting to URLs that themselves redirect, often because the old site already had redirects in place. Map every source straight to its final destination; our guide to redirect chains explains how to find and flatten them. Then update internal links to point at the new URLs directly, so the site does not rely on its own redirects to navigate.
Test the map before launch, not after. Load the redirect rules on staging and run every old URL through a crawler, checking that each returns a single 301 to the right page or the removal code you chose. A map with a few hundred rows takes minutes to check this way and saves weeks of chasing errors in Search Console later.
Launch day: completing the migration
With the map tested, launch is a sequence, not an event. Work through it in order.
- Take full backups of the old site, files and database.
- Update DNS if the host or domain is changing.
- Remove the crawl blocks you added on staging: robots.txt rules, noindex tags and any password protection.
- Enable the redirects, then test a sample from every section of the URL map.
- Update external links you control, such as social profiles and directory listings.
- In Search Console, submit both the old and new sitemaps, and for a domain move use the Change of address tool.
Submitting the old sitemap as well as the new one looks odd, but the reasoning is sound: it helps Google to recrawl the old URLs and find the redirects sooner. Step three is the one most often missed. A staging noindex that survives into production can quietly deindex a site, and it is easy to overlook because the pages look fine in a browser.
Monitoring after launch
The first weeks are about catching what the map missed. Crawl the new site, then crawl the old URL list and confirm every one returns the redirect or status code you planned. Watch Search Console for spikes in not-found errors and for indexing changes, and compare traffic by section against your baseline rather than looking only at the total.
Expect some movement. Semrush cites Search Engine Journal research finding that “it took sites around 17 months to regain their traffic” after a migration. That figure comes from one piece of research, not a forecast for your site; timelines vary widely with the size of the site, the type of move and how cleanly it was done.
That is also the limitation of any checklist, this one included. It reduces the risk of the losses you cause; it cannot guarantee your traffic holds, because rankings move for reasons unrelated to the migration, including algorithm updates that happen to land in the same month. Your baseline is the only way to separate the two. If traffic to mapped sections recovers and one section does not, the problem is almost certainly in that section’s redirects or content. If everything drops together, look at site-wide causes first, such as a leftover crawl block. Keep monitoring until the numbers settle, keep the redirects in place for the long term, and do not start the next big change until this one has finished bedding in.
Frequently asked questions
How long does SEO take to recover after a site migration?
It varies. Semrush cites Search Engine Journal research finding sites took around 17 months to regain traffic, but timelines vary widely.
What is the most important step in a site migration SEO checklist?
URL mapping. Every old URL needs a 301 to its new equivalent or a deliberate status code such as a 410 when the content is removed.
Should I submit the old sitemap after migrating?
Yes. Submit both old and new sitemaps so Google recrawls the old URLs and finds the redirects.
Do I need the Change of address tool?
For a move to a new domain, yes. Use Search Console’s Change of address tool alongside the redirects.
The takeaway Win the migration before launch. Baseline the old site, test on staging, map every URL to a 301 or a 410, remove the crawl blocks, and monitor against your baseline.
