Cross-domain canonicalization can be defined as the process of ensuring that all requests for content within a domain will be directed to the same server.
This is accomplished by making it so that every subdomain is redirected to the main domain, for example, www.example.com redirects to example.com, and subdomain.example.com redirects to the root domain.
In other words, Cross-domain canonicalization is a process to ensure that the user sees the same results regardless of where they come from and is often based on HTML unescape which unescapes the HTML entities that were escaped with special characters. The benefit this brings is SEO since search engines are able to properly index each page without any errors or omissions.
The problem is that some sites don’t take full advantage of this feature when it should be used, resulting in confusing web traffic.
Cross-domain canonicalization is the process of creating a single URL that can be shared across domains. When this is not implemented, then there are a number of risks that come into play.
There is the risk that your website could lose search engine traffic, plus additional risks including hidden safety issues and increased vulnerability to hackers. If you want to avoid these problems, now's the time to implement cross-domain canonicalization as soon as possible.
There are two main methods for implementing cross-domain canonicalization: redirects, and meta refresh headers. Redirects
With redirects, we instruct either our server or proxy to send HTTP requests through another domain (using an Alternate Domain Name) instead of the initial request. This method allows us to have clients visit different URLs than their original sources, while still maintaining the same content.
The benefit of redirecting against another domain is that it doesn't change the original source of information; all other factors such as cookies, page titles, etc., remain intact.
Example: Cross-domain canonicalization is the process of identifying similar domains and ensuring that these domains are dealt with uniformly to prevent conflicts. For example, if a company has an international website, but there is a separate web address for each country or region then they need to implement this policy to ensure that all regions are operating under the same base domain. Implementing cross-domain canonicalization can be very beneficial in many ways, one of the most important being SEO.
Conclusion: Cross-domain canonicalization allows for more flexibility in web design.