A third-party score (1–100) predicting how likely a domain is to rank in search engines.
Domain Authority (DA) is a score developed by Moz that predicts how likely a website is to rank in search engine results pages. DA is calculated on a logarithmic 1–100 scale, factoring in linking root domains, total links, and other metrics. A similar metric, Domain Rating (DR) from Ahrefs, measures the same concept. Neither DA nor DR are official Google metrics — they're third-party estimates, but they're widely used as proxies for site authority.
When building links or evaluating content partnerships, DA/DR helps you quickly gauge the relative authority of a website. A link from a DA 80 site carries significantly more SEO value than a link from a DA 20 site.
Forbes.com has a DA of 95. A startup's new blog might have a DA of 5. Earning a backlink from Forbes would have a major positive impact on the startup's rankings.
DA 50+ is generally considered strong. 30–50 is moderate. Under 30 is typical for newer or smaller sites. What matters more is your DA relative to competing sites.