What are referring domains?
A referring domain is a unique website that references your site via a backlink or redirects. Within the SEO community, analysts accept those referring domains have a strong correlation with ranking highly in Google.
How do they differ from Backlinks?
Any reference from a domain is considered a single referring domain and whether you have an infinite number of references or only one; it counts as a single referring domain.
How can I check my Referring Domains?
The easiest way to check your referring domains is by signing up for a free copy of Google Search Console. Registering your site gives many benefits and up-to-date data from Google’s crawl of the internet.
However, other third-party tools exist that offer even more advantages. They include metrics that indicate the quality of referring domains. These tools include Ahrefs, Majestic and Moz to mention a few.
How can I improve my Referring Domains?
Generally speaking, the best way to improve your referring domains is to continue building more of them toward your website. There are some quality metrics which are covered in this link building article.