A website migration occurs when a website moves from one environment to another, or there’s a change in regards to a site’s domain name. In SEO terms, whenever a fundamental change happens to the URL structure of a site, the move is considered a migration. Website migrations fall into several general types.
SITE MOVES TO A NEW CMS
Changing content management systems — also known as a CMS — is typically the most common migration type. A CMS is essentially a web application that sits on top of a database which stores all the information that you want on a website.
HTTP TO HTTPS
Google has been hinting at how important it will be for all websites to have extra security via an HTTPS configuration. Many in the SEO world theorize that this is already becoming one of Google’s many search algorithm factors. Google will never confirm specifics of how organic search rankings are determined, but HTTPS encryptions will become the standard for all websites in the near future.
If you decide to move from HTTP to HTTPS, then the same considerations apply to your domain as the other migration types. The domain name remains the same but an SSL certificate becomes associated with the site, and it looks something like this:
http://www.example.com —> https://www.example.com
SITE CHANGES DOMAIN NAMES
Whether it’s a company rebrand or a case where a stronger domain name is acquired, websites may choose to move to a new URL. If there is a change to at least one letter, number, character, or domain extension (eg. .com, .org, .net, etc.), this is a change which is applied to every page on a site.
Example: The website owner of example.com wants to rebrand his company and have his website moved to his newly acquired template.biz domain.
https://www.example.com —> https://www.template.biz
For this migration type, another example may include when one website is absorbed by another.
Example: The owner of example.com has a secondary company website which is too costly to maintain but still receives a good flow of organic traffic. He would want to set up the appropriate redirects to divert traffic from the lesser site to the main website to retain that traffic.