Traffic Drop After a Site Migration: What to Check, and in What Order

The store moved to a new platform. The new dashboard is simpler, the photos load faster, and the team signed off. Four weeks later, the line for visits coming from Google sits below where it was before the switch.

Whoever made the move says it’s normal and it will pass. Another agency, reached by phone, swears the redirects are wrong. Both could be right. Both could be wrong.

There is a way to find out. Google publishes what it expects from a site move, and it lists the mistakes it sees often. ¹ This piece follows that documentation in the order of a diagnosis. Along the way, I show what we did and measured when we migrated our company site in Brazil, with dates.

First, name what you changed

Think of a store on a busy street that moves. Sometimes only the landlord changes, and the door stays where it was. Sometimes the store moves to another street. Sometimes it stays on the same block and renumbers every shelf. And some owners do all of it at once, with a new facade.

Google splits these changes into two groups, with a guide for each. In the first, the address the visitor sees stays the same: a new hosting provider, or a move to a content distribution network. ² In the second, the address changes. That covers moving from HTTP to HTTPS, changing the domain, and changing the path, like a page that was /page.php?id=1 and became /widget. ¹ In Google’s documentation, this is called a site move with URL changes.

A platform change falls into the second group whenever the address format changes, even on the same domain. That is why the first question of the diagnosis is exactly what you changed.

1. Only the hosting, with the same addresses. The hosting guide applies. ²
2. The platform, on the same domain, with new addresses. Every old address has to lead to the new one. The Change of Address tool in Search Console stays out of it, because it does not cover path changes within the same domain. ³
3. The domain. Everything in the previous item, plus the Change of Address tool and a new Search Console property. ^{1 3}
4. The content and the structure, along with the move. Here Google itself warns you about the cost. ³

The warning sits on the help page for the Change of Address tool. Combining the move with a redesign of the content and the URL structure will probably cost some traffic. The reason, according to Google, is that it might need to relearn and reassess each page. ³ If you did all four at once, you have four suspects to separate.

What Google says is normal

The migration guide starts with what to expect. With any major change, rankings may fluctuate while Google recrawls and reindexes the site. ¹ On a medium-sized site, it can take a few weeks or more before Google shows the new addresses instead of the old ones. Large sites take even longer. ¹

The speed depends on the number of addresses and on how fast the server is. Submitting a sitemap helps Google discover the new pages sooner. ¹

The move happens one page at a time. For Google, it only ends when the crawler has visited every old address and every new one at least once. ¹ During that period, Google crawls the new site more heavily than usual, because requests to the old site are redirected there. The server has to hold up. ¹

On a hosting-only change, the pattern looks different. It’s normal for crawling to drop right after the switchover and then climb over the next few days, sometimes above the earlier level. ²

The guide to traffic drops closes the loop. If the drop came after the move and does not recover, Google tells you to look for common migration mistakes. ⁴ It gives no number of days to separate fluctuation from a problem, and I will not make one up either. Some checks, though, wait on no timeline at all. The yardstick and the staging block can be checked on day one.

Before hunting for the defect, check the yardstick

In the piece on why organic traffic dropped, the first row of the sheet is the door counter. That is the device that counts who walks into the store. In a migration, the door counter moves along with the store. And a freshly installed counter may count differently.

Google explains how its two dashboards differ. Analytics collects data through a tag installed on the site, so it depends on how that tag was installed. Some pages may be missing the tag. ⁵ Search Console shows data from Search itself, processed by Google the same way for every site. ⁵ On a platform change, the Analytics tag has to go into the new template. The Search Console click does not depend on it.

In my book, I describe the mirror image of this problem. A step up in traffic from AI showed up, and I almost celebrated. The domain had only entered the measurement account on July 2, 2026. What rose that month was the measurement coverage. ⁶ In a migration, the math can run the other way. A page left without the tag on the new site falls to zero in the dashboard, while people keep arriving. When the dashboard falls and the audience keeps coming, this is called a measurement drop.

The second suspect is the cookie banner. If the new site started asking for consent to track, and some people decline, Google warns that Analytics data gets skewed. ⁵

In our migration, both points showed up together. On September 2, 2026, the new site inherited the old site’s Google tag, loaded only after consent in the banner. ⁷ Before the domain switchover, the team found two defects that would have launched the site measuring nothing, with no warning. ⁷

The first was in the site’s own code checker. It expected an ID starting with “G-”, and ours starts with “GT-”. Measurement and the banner would have stayed off. ⁷ The second was at the hosting provider. The variable holding the ID was saved empty, and the command reported success. ⁷ Since September 8, an automated check opens the site every day. It confirms the tag and the banner in the code the server delivers. ⁷

I will state one limit. The record for the old site does not say whether it asked for that consent. So in our before-and-after comparison, the yardstick will be Search Console clicks.

The pair sum

The third suspect is still missing, and it fools even people who measure well. Think of someone who changes their cell phone number. For a while, friends keep calling the old number. Little by little, they switch to the new one. If you watch only one of the two phones, the calls seem to have vanished.

Search Console records the click on the address Google chose as canonical. ⁵ During the move, the old address keeps losing clicks and the new one keeps gaining them, as the new pages enter the index. ¹ The right comparison adds up both addresses of each page, before and after. I call this the pair sum. The name is mine, and the method comes straight from those two Google passages.

On a domain change, the pair lives in two Search Console properties. Google asks you to verify and watch both, and the expected pattern is the old one going down while the new one goes up. ¹ If you open only the old property, you watch the traffic go to zero. It went exactly where it should.

One last caveat about the yardstick. If your comparison crosses April 21, 2026, compare clicks only. On that date, impressions and average position showed a step change. It hit four of the five sites I measured, and clicks stayed flat. ⁸ The full exam of the instrument, with the cases I have seen, is the baseline exam in the SEO audit.

When the drop is real: what tends to break

If the pair sum fell in Search Console, and Analytics draws the same trend, the drop is real. ⁵ If the site disappeared from search altogether, the triage starts at case 4 of the piece on a site that isn’t showing up on Google.

The migration guide lists the common mistakes, the ones that keep the new site from being fully indexed. ¹ Together with the preparation advice on the same page, they fit into six checks. The order is mine: it runs from what brings down the whole site to what brings down only a little.

1. The “under construction” sign nobody took down

Picture an “under construction” sign hanging on the door of the new store. It protected the remodel. On opening day, someone has to take it down.

On a website, that sign is the staging block. Some site owners block crawling in robots.txt, or mark pages with noindex, while the new site is in development. ¹ Google puts forgetting those blocks at the top of its common mistakes. ¹ The hosting guide says to remove any temporary block before you point the domain. ²

A forgotten noindex takes pages down slowly. A misplaced noindex rule removes pages as the crawler reaches each one. ⁴ To check, open the new site’s robots.txt. Then run the Search Console URL Inspection tool on the pages that seem to be missing. ¹ If the new site runs on WordPress, a single box in the dashboard can apply this block to the whole site. It is explained in SEO for WordPress.

2. The old address with no destination

Every old address has to lead to its new equivalent, with a permanent server-side redirect. ¹ The guide asks for three more precautions. Go straight to the final destination, with no long chain. Do not send many addresses to the homepage, which may be treated as a soft 404. And return a 404 or 410 for content that did not make it to the new site. ¹

Google writes that it frequently sees redirects pointing to addresses that do not exist on the new site. ¹ To find them, it suggests checking whether Search Console shows an unusually high number of “Not found” errors. Another route is to crawl your own site with a tool like Screaming Frog. ¹

In our migration, the redirect table was tested pair by pair, and every pair reached a live page. The list of addresses Search Console knew about found five old pages returning a 404, outside the table. ⁷ That case, and the four other places where our redirects failed silently, are in 301 redirects.

3. The stamp that still points backward

Every new page needs a canonical URL pointing to itself. ¹ Once the redirects are in place, the guide says to check that the new site’s canonical tags use the new addresses. ¹ A site with versions in other languages has one more line to change, the hreflang annotations. ¹

When a page arrives imported with the old site’s canonical, or the staging address, it tells Google another page is the original. The redirect points forward, and the canonical points backward. To check, open the code of three important pages and look for the rel=“canonical” line.

4. The drawers that arrived empty

Picture a move where the dresser arrived in one piece and the drawers came empty. Nobody notices on moving day. You notice when you go looking for the scissors.

Google’s guide reminds you to move images and downloadable files, such as PDFs, because they may already get traffic from Search or from links. ¹ Videos, images, JavaScript, and CSS embedded in the pages also belong in the move plan. ¹

In our migration, the empty drawers showed up on September 3. A PDF from the old site returned a 403, and an Instagram automation was still sending people that link. The address got a redirect to the page that now delivers the same prompt. ⁷

That same day, a reader complained that the link did not bring the promised prompt. The redirect worked. In the rewrite, the new article had lost the prompt the old one carried at the top. ⁷ The page got a new section, with a prompt of its own, that same day. ⁷ The address led to the right place, and the reason for the visit was missing there.

5. Internal links and sitemap on the old address

An internal link pointing to the old address keeps working, because the redirect passes it along. Even so, every click goes through one extra hop. Google notes that redirects are slow for users, and asks you to update your own links using the URL map. ¹

The sitemap has to list the new addresses, and forgetting to update it is among the common mistakes. ¹ Once submitted in Search Console, the new sitemap helps Google learn about the new URLs. ¹

On September 3, the production audit of our site checked 81 internal links and 78 sitemap addresses. All of them returned a 200 directly, with no redirect along the way. ⁷ The day before, Search Console still had two WordPress sitemaps registered. One of them already returned a 404. ⁷

6. What lived in the old template

Some things never show on the page, because they live in its template. Search Console verification is one. If the property was verified with an HTML file, a meta tag, or the Analytics tag, the new site has to carry the same proof. ¹

Structured data is another. It is the markup that tells machines what the page and the company are. On WordPress, SEO plugins like Yoast and Rank Math list this markup among their features. ⁹ When you leave WordPress, the plugin stays behind, and the markup goes with it unless someone rebuilds it.

On our new site, the markup comes from a single generator. On September 10, Google’s Rich Results Test flagged the publication date as missing a time zone. Since the date came from the generator, the defect applied to every page, and the fix was made at the source. ⁷ The test shows which rich result types it found on the page, and the errors for each one. ¹⁰

Our case, from start to finish

Our company site in Brazil, seogenome.com, moved off WordPress in early September 2026. The new site is built in Astro and hosted on Vercel. The domain stayed the same, and the addresses changed. ⁷ By Google’s classification, it was a site move with URL changes within the same domain. ^{1 3}

What I still do not have is a traffic number for the migration. As I write this, on September 14, the switchover is twelve days old. Google itself talks about weeks for a medium-sized site. ¹ A twelve-day curve would show the start of a path Google describes as fluctuating. That is why it stays out.

When the comparison comes, it will follow the method in this piece. The Search Console property is the same before and after, because the domain and the host did not change. ⁷ The yardstick is clicks, summed by address pair, against the snapshot of August 31. In my book, I insist on taking the before picture under the same conditions. Different conditions produce a different screen. ⁶

The migration sheet

Take a sheet of paper and draw the rows below, in order. In each row, write down what the dashboard showed and the date.

The sheet has a single rule. If row 1 lights up, fix the instrument before reading any number in Analytics.

What you do with the answer

Each row calls for different work. A broken yardstick gets fixed at the instrument, and the site stays as it is. A staging block gets removed, and recovery follows the pace of crawling. ¹ An address with no destination needs the right pair. An empty drawer needs its content back.

If an agency handled the migration, the sheet also serves another conversation. Deciding whether to hire again? What to check in the previous work is in hiring SEO again.

From now on, when someone tells you the drop after a migration is normal, you will ask for two things. The date of the switchover. And the pair sum in Search Console.

The first step fits into today. Open Search Console, export the pages from the last 16 months, and pick the twenty old pages that brought the most clicks. Next to each one, write the new address.