Subdomain to Main Domain Site Migrations

Google’s John Mueller was asked about migrating a subdomain to the main domain. His answer explained why this kind of site migration can be difficult to do. He explained what to look for in order to increase chances of success.

Moving from Subdomain to Main Domain

The person asking the question shared the background information that the subdomain of the site has been around for decades. She explained that it is the most important part of the site.

Because that section of the site is so important she was concerned about avoiding any negative impact from migrating the subdomain content to a new location within the main domain.

She also mentioned that the topic of the subdomain was politics and daily life issues like public health policy.

John Mueller’s answer focused on what to watch out for in general about moving from a subdomain to a main domain.

However the last part of his answer consists of additional advice related to the Google News side of publishing.

Subdomain Migration: Hard to Know Exact Outcome

John Mueller paused for a moment to think about his answer.

His thoughtful pause gave the impression that the answer was complex and that he was taking a moment to organize how to best answer the question.

John Mueller Pauses to Think About His Answer

Google’s John Mueller pauses to think about his answer to a subdomain site migration answer

When he answered, John paused a couple times, again giving the impression that this was a tricky question to answer.

The reason may have been because the main point of his answer was that the outcome of a subdomain to a main domain migration is more uncertain than a one-to-one site migration from one domain to another domain.

John Mueller answered:

“Uhm… I… I think you can do this
…

So… let me see… uh…

See… I think…

One of the key aspects here that uh… is important here when you’re moving from a subdomain to the main domain, to a different directory for example, is that we need to look at the new website overall and kind of reevaluate the overall situation.

And that means that it’s hard to know ahead of time what exactly will happen.”

I think it’s important to underline that the issue with a subdomain to a main domain migration is that, according to John, it could trigger a reevalution of what is now, according to Mueller, a new website.

Whereas in a one-to-one site migration there is no need to reevaluate the entire site because the site remains the same.

Subdomain Migrations: It’s Hard to Know Exactly

Mueller continued his answer, affirming that the outcome of a subdomain to main domain migration can be hard to know exactly.

“And it’s something where you can use your knowledge and your experience to figure out a little bit what possibly could happen.

But it’s hard to know exactly because if you move from one domain to a different domain then it’s easy for our systems to say, take everything here and and just copy it over here.

But if you move from a subdomain to a main domain, you’re essentially merging different parts of the website.

And that final outcome that you have, will depend on your final structure.”

Plan Subdomain Migration Ahead of Time

Mueller next encouraged planning ahead of time by mapping the site migration from the old location to the new location in the main domain.

Mueller also suggested, in general terms, the value of mapping the old domain prior to the site migration in order to validate the success of the subdomain migration.

In my opinion, it may be useful to create a map of the old subdomain structure with a crawling tool like Screaming Frog, create the 301 redirects after the site migration, and then do a full crawl of the old subdomain to make sure that all the 301 redirects are in place and to investigate any 404 page not found response as signals of a possible mistake.

Mueller continued his answer:

“So, I think overall it’s something where you can do these kinds of changes.

But you have to watch out that you do them in a reasonable way.

And what I would recommend doing here is making sure that you have a very clear mapping of your old website to the new one and then really checking all of those old URLs.

You can use… there are various tools to test that.

But really make sure that everything is moved properly.

And then double-check by crawling the main domain again separately to make sure that really, your new website structure is okay and all of the pages can be found.

And for the most part, I assume that that will be fine.

I mean, it’s possible to do other mistakes as well. But those are usually the more common types of issues.”

Unclear on How Long Migration Effects Will Linger

Every site is different in terms of topic, size and how that topic fits into the website overall. John was understandably vague about how long the site migration would take until things settled down.

Mueller explained:

“I don’t know what I would recommend in terms of how long this will take or what the final effect will be.

I suspect maybe you’ll see an effect for a couple of weeks until things settle down.

But it should be possible.”

Site Migration Advice for Google News Publishers

Mueller next shared advice that was specific to Google News publishers:

“If you’re a Google News publisher, then I would also make sure that you contact whoever on the Google News site that is appropriate for you, in the Help Center for Google News publishers.

There’s also a contact form, just to let them know that you’re moving from this set of URLs to a different set of URLs.

Sometimes they need to make some changes in the Publisher Center… I don’t know all of the details there.

But just kind of to make sure that they’re aware of this as well.

But otherwise for search itself, making that move, making sure everything is lined up, is essentially what you need to do.”