Domain Authority is a third-party invention, not a Google metric. The capitalized term “Domain Authority” was created by Moz as a predictive score, and other SEO tools publish their own near-equivalents under names like Domain Rating or Authority Score. Google does not produce, publish, or use any single “domain authority” number, and Googlers have said plainly over the years that there is no one internal site-wide authority score that ranks pages. So when the title asks Google-metric or third-party invention, the verdict is clear: third party, and Google does not look at it when ranking your pages.
That matters because the name fools people. “Domain Authority” sounds like an official measurement of how much Google trusts your site, so site owners watch the number rise and fall as if it were the scoreboard. It is not. It is a tool vendor’s best guess at how a domain might perform, built largely from link data the vendor crawls itself, and it can diverge from your real Google performance in either direction. A page can outrank a higher-DA competitor every day, because the score that actually decided the result lives at Google and was never that number.
The nuance worth keeping is that Google clearly does use domain-level trust signals. It evaluates a site’s overall reliability, its history, the quality and pattern of links pointing to it, and its track record on a topic, and those things absolutely influence how readily new pages from that site rank. So the domain-trust mechanism is real even though the single tidy “domain authority score” is not. Third-party metrics are useful precisely because they try to estimate that real trust, which is why they correlate with results at all, but the estimate is not the thing itself.
In practice, treat Domain Authority and its cousins as a directional comparison tool, never as a Google ranking you are trying to satisfy. Use them to size up competitors and watch your own link profile trend, but make decisions from your actual rankings, traffic, and the quality of links you are earning. Stop reading a third-party score as if Google issued it, and you will stop optimizing for a number that does not appear in the algorithm.