The Guardian, a huge UK newspaper, posted a story named How the Guardian successfully moved domain to www.theguardian.com.
Yes, The Guardian migrated content from www.guardian.co.uk, m.guardian.co.uk or www.guardiannews.com to one domain name, www.theguardian.com. A scary thing for such a big publisher for many reasons, but especially for things you don't ultimately control - search bots and search traffic.
The outcome was a small dip in traffic early on but record breaking traffic shortly after throughout today.
My company has done tons of site migrations, honestly, I don't sleep at night the day before a big launch. But there are technical outlines you can take to minimize the risks of these types of migrations. You test and test and test and when confident, you pull the trigger. Then you analyze the data almost hourly to make sure you didn't miss anything in your tests. Ultimately, virtually all of these migrations do go as planned but they are scary - I'll be honest, very scary.
Joost de Valk from Yoast helped The Guardian on the SEO front make the switch and he got a sweet call out from them:
The Guardian site receives a lot of its traffic via referrers. We had to make sure that those referrals continued to the new domain. We attempted to speak with all our major referrers including search engines and social media. We read their official blog posts and implemented their recommendations. We audited our sitemaps and HTML tags. We released any changes we made before the domain move so that we could see their effects in isolation. We improved our page speed (time to first byte) by using Fastly’s CDN. We wrote page crawlers which reported dead links or chained redirects and fixed them. In short, we set about removing as many obstacles to robots crawling our site as possible. We did all of this with a tremendous amount of help and direction from SEO expert Joost de Valk and the Guardian’s excellent SEO team.
But in the end we still had no guarantee that these changes would help mitigate any loss of traffic from referrers. The effect of the domain change was still unknown.
It pains me to see people come to me and tell me they lost all their traffic months later after a switch. There are so many basic things you can do to minimize the traffic loss and plan for improved search engine visibility at the same time. Yes, it takes a lot of time, practice and testing - but it is all doable.
Google's John Mueller shared this on Google+ and said "I know site-moves are always scary for webmasters & SEOs of larger sites, but here's a positive story from a big news website." It is important for SEOs to know that yes, it is scary but the outcomes can be great.
Forum discussion at Google+.