Domain Migration:
An SEO Case Study

by on 17th September 2010

Imagine the moment: Your client calls to let you know they’ll be changing their domain name, and that they need an SEO strategy to maintain their SEO visibility. Now imagine that particular client happens to be in a high competition niche: car loans. It’s the kind of thought that can keep you awake at night!

We’ve recently survived a domain migration project covering exactly the situation above. A high competition market, with a subdomain to full domain migration. That’s “*” to “”. With the very kind permission of the client in question, I’m going to share the methodology we used.

Charting visibility

OLD Site SEO Visibility

The first and most important step in any SEO project is to start collecting data, early. I’m a big fan of the search engine visibility metric as an aggregate measure of the health and performance of a website.

This chart shows a daily search engine visibility percentage for the old domain. Don’t panic about the drop in visibility! That was intentional. To get this data we use Advanced Web Ranking, collecting ranking data for both the old and new domain names.

The keywords selected are the top 100 highest traffic driving terms in For a migration, monitoring terms already driving traffic to the site seems much wiser than the more aspirational “industry top terms” that we monitor visibility on an ordinary SEO project.

Visibility (Old vs New)

visibility seo small

This chart, with it’s daily update (7am, every morning for the last month – the first email I’ve checked every day!) shows what’s been going on. The green line is the new domain visibility – though the chart doesn’t show it, the new domain actually outranks the old by a few tenths of a percentage. The symmetry is amazing, in the past 30 days I’ve found this chart to be so fascinating.

You’re viewing this correctly: No drop in visbility using a site wide 301 redirect to a new domain.

Plan your migration

Before you make any changes, it’s wise to create a domain migration plan. We created a step by step, timeline of events with checks and conditions that should be met before progressing to the next stage. The plan was researched (it’s been a long time since I read Google Webmaster documentation so closely!), documented and discussed with the clients. Given their pivotal role in all of this, we quickly built a close working relationship with our clients and made sure the plan was understood by all parties involved.

Think about the variables

When a domain changes, what are the variables? What are the flags that might tell a search engine that something huge has changed? What if such a thing as a “bait and switch” filter exists that could catch us out with a perfectly legitimate domain change? There were more questions raised than this, but you can probably see an insight into my thought process while the migration plan was being hatched.

If you understand all of the variables, you can plan to change them one variable at a time. It’s variables that can make or break a domain migration. In my opinion, these are the most important:

  • Old and New domain WHOIS details
  • Host IP
  • Content
  • Most “powerful” links by PageRank and mozRank
  • Highest traffic driving links

We decided to try and change as few variables at any one time through the process. If anything went wrong we’d have a fighting chance at identifying the cause of the issue and resolving it quickly.

A step by step overview

Broadly speaking, we planned to change the domain first, making sure the hosting IP, WHOIS and content all remained unchanged. As a group, we agreed to review changes in visibility daily and watch closely for changes. Here’s a step by step breakdown of what we did at the point of migration:

  • Kept site content exactly the same (more on this later)
  • Matched the WHOIS to be exactly the same as the old domain
  • Kept the host IP stayed the same
  • Created a sitemap xml file at the same URL on both domains
  • Submitted the old sitemap file a few weeks before transition
  • Submitted the new XML sitemap file as soon as the domain went live
  • Pinged Bing and Google with the old sitemap XML file URLs, being sure that the old sitemaps would respond with a 301 redirect to the new files

Link realignment

We’d prepared a list of the highest traffic driving links prior to the migration. This list also included high PageRank / mozRank links too. We’d made contact with as many webmasters linking to the site as possible, informing them that we were going to change the domain over in the near future. This made the actual changes a lot smoother, and webmasters were informed when the domain swapped over (and were asked very politely to change the links over!).

Webmaster Tools – Change of address

change of address in Google Webmaster Tools - Subdomain

To my surprise, there is no change of address feature for subdomains in Google Webmaster Tools. If you’re writing a migration plan involving a subdomain redirection, don’t count on Webmaster Tools for help. Why Google have taken this option I really don’t know.

The final step – content

Part of the project was to launch a new website. We deliberately decided to hold on the content changes until the domain had migrated smoothly. Prior to the new site going live, we meticulously crawled the site using a URL list created from the original domain. Checking that each URL responded with a redirect and ultimately took our crawler to the appropriate page, we launched the new site with a sense that errors would be kept to a minimum, and the redirects would continue to do their work.

Post migration thoughts

The process went smoothly, much to everyone’s relief. A domain migration is not to be taken lightly, and planning your steps can help relieve some of the worry that your site could lose its rankings. With that said, all the planning in the world still needs a little luck to help things run without a hitch.

For me, I found the symmetry in the visibility shift amazing. There was a moment (for about 2 hours last weekend) where both domains ranked quite well. It was almost as if two indexes were being merged into one, a potentially fascinating insight into Google’s index consolidation and management process. I’m glad we’ve been through this migration, and I’m actually really grateful for Google’s level of documentation on the topic. So few SEO blogs have a decent guide to the subject, it’s quite alarming!


  1. I completely agree on not relying on GWT for any help in this process if anything I would avoid it next time I do a domain migration.

    I think they introduced the change of domain name just to help them filter out the less than genuine 301 redirects out there.

    As well as swapping the old links, I would also add that getting a few decent links straight after the 301 to the new domain would help also.

  2. Thanks for sharing Richard. It all seems to have migrated rather quickly, so well done you!
    We recently moved from a strategy to a .com/uk strategy for a global site, but we are experiencing problems with the US site “interfering” with UK results due to Google’s inability to distinguish the two properly so I fully support your approach of not being too dependent on Webmaster Tools… wonderfully useful as it can be.

    Anyway… No drop in visbility using a site wide 301 redirect to a new domain is very encouraging indeed.

    I’d be interested to know what your “strike rate” was in getting webmasters to switch over the links?

  3. I switched a domain over with a 301 and it actually seemed to clean the penalties of the domain and it started ranking again

  4. Great post, really helpful. Thanks a lot for sharing your knowledge.

  5. Great post. Thanks!
    4 Cores Comunicação

  6. Interesting on the sub-domains not being transferable in GWT. Wonder what that says about how Google views sub-domains!

    Would also be interesting to know about coverage of the two sites during the process; for instance, how Google’s site: command responded during the migration (or even better to have server logs that show bot activity) and were the same pages (albeit on different domains) being returned during the process?

  7. Thanks for the road map of how to do it correctly. I have wanted to change a url for quite some time, but I am always discouraged by the horrible rumors of what can happen. Glad to know it can be done successfully.

  8. Hi Chris,

    The subdomains thing in WMT was a really big surprise. Why Google have a blank page without much of an explanation disapointing to say the least. Glad you enjoyed the read and thanks for stopping by!

  9. No problem! If you’re about to do the same type of move let me know how it goes.

  10. Just the thought of switching domain names makes me physically ill. I don’t think I could do it but…it happens all the time with spin offs, mergers, etc. The site wide 301 must make your clients go whew….thank goodness!

  11. All of these make sense to me except the Host IP. I can’t imagine that your results would be any different had the Host IP changed. Let’s assume you needed to switch hosts because of bandwidth issues for the website – your IP would change in that circumstance. I’d like to see another test where the Host IP changes and see the difference in the two graphs.

  12. Great post Richard you have put some really useful information that will help many in their own Domain Migrations. I would stress the importance of 301 redirects of files when it come to doing things like this.

  13. Hi Kenneth – thanks buddy. Yes – my personal opinion is that as long as the links are realigned, the WHOIS is sorted and the 301s are handled nicely, it is absolutely possible to move to a new domain without a hitch. Good luck with your migration!

  14. question for you – I would like to do this with one of my sites; the current domain name is getting some favor due to it’s age (2004), but if I change to a newer (but more SEO friendly) domain name (only 1 yr old) am I going to see a drop? Or does the 301 completely transfer everything over. Sorry it’s late and I’m not thinking clearly. I don’t bookmark many blogs, thanks for this great resource, I’m loving it :)

  15. We’ve been through this with one of our sister websites in the last month. It can be a pretty daunting and stressy process to say the very least and it helps if this is being done with a webmaster who knows what they are doing!

  16. Great Post! A real guidelines to follow, Thanks a lot

  17. Hi Richard,

    Just want to ask, how did you inform all the staff about the change in domain. What important details should be in the communication email?

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