How to migrate a domain without losing your SEO

1. Map All Old Domain URLs To Their New Domain Versions 

This basically required mapping all of the dynamic and static old domain URLs to new domain URLs so they could all be 301 redirected at launch.

2. Understand How Any UI Changes Might Affect SEO 

Changing UI while changing domains should be avoided whenever possible to eliminate yet another thing that could go wrong. That said, if you are going to change the UI, you need to make sure that the links, text, images and other elements are considered for their SEO impact.

3. Reduce Or Eliminate 404 (Not Found) Errors 

You’ll want to do this regardless of whether or not you are changing domains, but when you make the switch, you’ll want Googlebot to be able to crawl the site quickly and effectively. URL errors can slow down Google’s ability to find all of the URLs on both the old and new sites, so you’ll want them gone before you do anything. Typical fixes included: Identifying patterns that were causing 404s and deploying fixes. Where it made sense, changing 404s to 200s and using rel=canonical tags to canonicalize them to active, relevant pages. Removing broken links from the UI. 301 redirecting outdated URLs to active pages when there was a high degree of relevance. The majority of “Not Found” errors were identified by using the following tools: Reviewing Google Search Console’s Crawl Errors Report. Crawling the site with text browsers such as Screaming Frog and Xenu. Using the broken inbound link reports in backlink analysis tools like Majestic.

4. Figure Out Your Subdomains

We identified all existing subdomains and tagged each as “kill” or “keep.” Subdomains that were worthy of making the leap to the new domain were redirected. Those that didn’t make the cut were deprecated with a 301 redirect to a new, relevant page or area of the site.

5. Clean Up Your XML Sitemaps 

Once XML sitemaps on sites with millions of URLs are deployed, they typically get ignored by developers who often have better things to do than worry about a huge file that often was built by someone else three years ago with god knows what kind of logic. As with the subdomains, the migration finally gave us a good justification to go in and figure out how to map sitemaps to the new domain while getting rid of superfluous files.

6. Figure Out Your Canonical Links

The decision was made to canonicalize as many corresponding similar pages as we could identify to try to tighten up the site against potential Panda issues. All canonical links that had been previously implemented on old domain were identified and mapped to the new domain and relevant pages. All of this data was shared with the team via a Google Spreadsheet that could be easily updated and disseminated quickly.

7. “Warm Up” The New Domain

In my experience, migrations to new domains that either have never been indexed by Google or have few or no backlinks are the ones that typically get hit the worst when they are launched. With that in mind, old domain set up new domain several weeks before launch and posted new content to the site once a week to help get a jump on being indexed by search engines. The content was general and not connected to the old domain brand, so it wouldn’t be associated with old domain before the big reveal.

Source: https://www.nilebits.com/blog/2019/01/how-to-migrate-a-domain-without-losing-your-seo/