Domain Rating (DR) is a quality metric developed by SEO tool company Ahrefs.com to determine how authoritative a domain is based on its backlinks. It is visible in the majority of reports produced by Ahrefs. Domain Rating takes into account both the quantity and quality of the links pointing to a domain. 

DR is measured on a logarithmic scale from 0 to 100, with the higher scores denoting a more authoritative site. Being logarithmic means that the higher your DR gets, the more challenging it will be to grow it by another few points.

Ahrefs looks at a number of factors when calculating the domain rating of a site, these include: how many unique domains have at least 1 followed link to the target site, the domain ratings of the linking domains and how many unique domains each of the backlinking sites link out to. These values are incorporated into their algorithm and the result is plotted on a dynamic 0-100 scale which ‘stretches’ over time. 

It’s this dynamic ‘stretching’ over time that may see your Domain Rating decrease despite your site having retained all its backlinks. This change is because other sites have gained a lot of backlinks. A site that already has DR 100 can not increase its domain ranking, so when it gains more links the entire scale has to be reshuffled to accommodate this increase. 

It’s worth noting that if a site with a high Domain Rating links to thousands of other sites, Ahrefs values their links less, however, if a site with a lower Domain Rating only links out to a few sites, Ahrefs consider those links quite powerful. Domain Rating doesn’t solely rely on the number of highly-rated domains that link to you; it also takes into account how many other websites these highly rated domains link to. 

Ahrefs describes Domain Rating is not a measure of a website’s quality and legitimacy and is not a ranking factor used by Google. You cannot rely on Domain Rating alone in determining if a website is spammy or not. However, it can give an indication that a domain has weak links in its backlink profile that don’t pass enough authority.