A protocol change would be changing a website from HTTP to HTTPS.
Subdomain or Subfolder Change
When a firm decides to move from one ccTLD into subdomains or subfolders. For example, www.example.com.au becomes www.au.example.com or www.example.com/au
Domain Name Change
This is common when a company is rebranding and has to migrate from one domain to another. For example, www.example.com to www.sample.com
Top-Level Domain Change
This occurs when a company decides to expand its business internationally or limit to a single country. For example, www.example.com to www.example.com.au and vice versa.
Site Structure Changes
These are changes to the site's layout that often impact the internal reference and URL structure of the page.
This occurs when a website is moved from one platform to another. For example, migrating from WordPress to Shopify.
Mobile Setup Changes
Partial website migrations include things like switching to a mobile configuration, indexing apps, and developing a PWA website.