BACKLINK METRICS
DR, DA and Authority Score are not the same thing.
Ahrefs Domain Rating, Moz Domain Authority and Semrush Authority Score are third-party metrics designed to summarise aspects of a site's backlink strength or broader authority. Google does not publish or use these proprietary scores.
Domain Rating is an Ahrefs metric
Ahrefs describes DR as a relative 0–100 measure of the strength of a website's backlink profile. It is useful for comparisons, but it should not be read as a quality certificate or a Google score.
Domain Authority belongs to Moz
DA is Moz's predictive metric. Its calculation and data source differ from Ahrefs, so a site's DA and DR should not be expected to match.
Authority Score belongs to Semrush
Semrush combines link signals with estimated organic traffic and checks for suspicious profile patterns. Again, it is a proprietary metric, not a search-engine grade.
Why the scores can still be useful
They make it quicker to compare large groups of sites and spot candidates worth investigating. They are especially useful when paired with referring-domain counts, organic traffic, topical relevance and manual backlink review.
What they cannot tell you alone
A high score does not prove a site is trustworthy, relevant or worth buying a link from. Scores can also lag changes or be distorted by unusual link profiles.
Compare like with like
Use one provider's metric consistently when comparing competitors. Do not treat DR 40, DA 40 and Authority Score 40 as equivalent measurements.
References: Ahrefs DR documentation and Semrush Authority Score documentation.