Most traffic drops after a migration aren’t caused by Google punishing anyone. They’re caused by someone forgetting to redirect a URL, or assuming a redesign and a domain change could happen at the same time without consequences. The site looks better, but the rankings don’t come back for months. Nobody planned for that gap, because nobody expected it.
Migrations have a reputation for being risky, and that reputation is earned. A migration can immediately affect organic traffic, referral links, and other channels that contributed to the old URL’s authority, since all of that has to be reset around the new destination. The risk lies in how many small technical decisions have to be made correctly, in the right order, before launch day. This article looks at how leading SEO companies approach site migrations, and why the ones that go smoothly usually look boring from the outside.
Not Every Migration Is The Same
People use the word “migration” to describe all kinds of website changes, which is where things can get a little confusing. Moving to a new domain, switching from HTTP to HTTPS, rebuilding on a new CMS, changing your URL structure, or combining domains can all be called migrations. But there’s one question that matters more than the label: Are the URLs people see actually changing?
If they are, you need to account for every old URL and decide where it should go. That usually means building a redirect map and putting the right redirects in place. If the URLs aren’t changing, you’re dealing with a different type of project, and you shouldn’t automatically follow the same process.
This distinction also matters when it comes to Google’s tools. The Change of Address tool, for example, is meant for moving a site from one domain or subdomain to another. It’s not something you’d use for a change like moving pages around on the same domain or switching a site from HTTP to HTTPS. Teams that reach for the same checklist regardless of migration type tend to either overbuild simple moves or underbuild complex ones. Knowing which kind of migration you’re actually running is the first real decision, and it’s one a lot of in-house teams skip past.
The Redirect Map Is The Whole Project
Everything else in a migration supports one thing: making sure every URL that mattered on the old site has somewhere relevant to go on the new one. Google’s own guidance describes generating a list of old URLs, and the recommended sources are practical rather than exotic. Sitemaps, server logs, analytics, the Links to your site report in Search Console, and the CMS itself are all reasonable places to pull that list from, starting with the URLs that carry the most traffic and the most links.
Strong teams treat this mapping exercise as the actual deliverable of a migration, not paperwork that supports the “real” work of building the new site. A wildcard redirect from the old domain straight to the new homepage is tempting because it’s quick and easy. But in most cases, it’s a bad idea. Someone who clicks an old page expecting a specific piece of content could end up somewhere completely unrelated. Search engines see the same mismatch, and you risk losing the relevance and context that helped that old URL rank in the first place.
It takes more work, but mapping old URLs to their most relevant new destinations is the safer approach. A proper one-to-one redirect map gives you a much better chance of holding onto your rankings while also making sure users actually land where they expect.
Redirects Are Not A One-Time Setting
Once redirects go live, the instinct is to move on. That instinct is premature. Redirects need to stay in place for at least 180 days after a Change of Address submission, longer if traffic is still arriving through them from Google Search, and there’s no real downside to leaving permanent redirects active indefinitely.
There’s also a resourcing detail that gets missed until it becomes a problem. After a migration, Google will temporarily crawl the new site more heavily than usual, since traffic redirected from the old site adds to the crawling the new site would normally receive, which means the new site’s hosting needs enough capacity to absorb that spike. A migration that goes down under crawl load in the first week creates a worse signal than a slow, careful reindex would have. Experienced teams flag this with hosting providers ahead of time instead of finding out during a traffic graph.
Ranking Drops During A Migration Are Not Automatically A Failure
One of the harder things to communicate to a client is that a temporary dip is expected, not evidence that something went wrong. With any significant change to a site, ranking fluctuation during recrawling and reindexing is normal. The question worth asking isn’t whether rankings moved. It’s whether they’re recovering on a reasonable timeline, and whether the pages that dropped are the ones tied to actual technical issues rather than just noise.
This is also where patience gets confused with negligence. Google representatives, including John Mueller, have addressed this directly in response to a site owner who was frustrated by a slow recovery after a migration. The “Mark as fixed” feature in Search Console doesn’t make Google reprocess or recrawl a site any faster. It simply updates the status of the issue you’ve flagged.
In other words, clicking the button won’t make Google crawl the site any faster or speed up recovery. Google still needs to recrawl and reprocess the affected pages on its own timeline. That’s why experienced teams focus on what they can actually control: checking that the redirects are working, making sure the right pages are being indexed, and looking for real issues. Repeatedly clicking buttons in Search Console might feel like you’re doing something, but activity isn’t the same as progress.
Stacking Changes Makes Every Problem Harder To Diagnose
The single most common mistake in migrations that go badly is trying to do everything at once. A domain change, full redesign, content overhaul, and new navigation might seem like an efficient way to get everything done in one go. But if rankings drop afterward, you’re left trying to figure out which change caused it.
An SEO migration and a rebrand are really two separate projects that happen to have the same launch date. If you can, it’s better to separate them. If you can’t, you need a way to isolate the different changes so you can work out what’s actually responsible if something goes wrong.
That’s what makes a difficult migration diagnosable instead of a guessing game. When evaluating an agency, don’t just ask how they’ll prevent a ranking drop. Ask how they’ll figure out what went wrong if five major things change at the same time. A good agency should have a clear answer.
Domain Consolidations Need To Be Declared, Not Assumed
Large sites sometimes carry more domain variants than anyone tracks closely: a www and non-www version, an old acquired domain, a regional subdomain that never got folded in properly. Google’s systems don’t automatically infer that redirecting one variant, like www, means a related variant, like non-www, has also completed its migration at the signal level. Each variant needs its own declared move.
This is a detail that’s easy to miss because the redirects themselves might all be technically working. The gap lies in whether Google has been told, through the right channel, that the move happened. A property that exists in Google’s index but was never verified in Search Console can’t have a Change of Address submitted for it at all, which leaves a real gap in the migration signal even when the physical redirects are already in place. Teams running consolidations across multiple legacy domains need to check this variant by variant, not assume one submission covers everything.
What To Ask Before Trusting Someone With A Migration
A migration is one of the few SEO projects where a mistake is immediately visible and expensive to reverse. Before you hand a migration over to an agency, ask them how they’ll actually build the redirect map. Don’t settle for a simple “yes, we’ll handle it.” If you’re planning a redesign at the same time, ask how that changes their approach and whether they’d recommend doing both together or suggest keeping the projects separate.
It’s also worth asking how they’d handle a ranking drop three weeks after launch. What would they check first? What would they tell a nervous client? A good agency should be able to walk you through the diagnosis rather than immediately offering reassurance.
A site migration is largely won or lost before launch. What matters most is getting the basics right: building a solid redirect map, keeping the migration separate from other major changes where possible, and giving Google enough time to recrawl and reprocess the site properly. Those things will have a much bigger impact than any single technical trick. Rankings dip during most migrations. What separates a good outcome from a bad one is whether the team running it can tell the difference between expected fluctuation and an actual mistake.
The agencies that handle migrations well aren’t the ones promising a seamless transition with no dip at all. The right agency should be able to tell you exactly what they’ll monitor in the weeks after launch and, just as importantly, how they’ll distinguish a genuine problem from the normal fluctuations that can happen while Google reprocesses a site. If you’re looking for help with a migration, take a look through our vetted list of SEO agencies and find a team with real migration experience.