Domain authority

Domain Authority with capital letters is Moz's metric, scored from 1 to 100. Other tools have their own versions, such as Ahrefs' Domain Rating and Semrush's Authority Score. Each is calculated differently from that company's own crawl of the web, so the same site gets different numbers from different tools.

Google has said it does not use these third-party scores. A higher third-party score does not cause better rankings; at best it correlates with the links that help.

How it works

The tools crawl the web, record the backlinks each site receives and model how strong that link profile is compared with others. The score is relative and logarithmic in most tools, so going from 20 to 30 is much easier than going from 70 to 80, and scores can drop when the tool recalibrates, even if nothing changed on your site.

Google's own systems judge individual pages and sites using many signals, including links, relevance, content quality and experience and trust. None of that is visible as a single number. Because each tool only sees links from its own crawl, scores can also be gamed. Some sellers inflate a site's score with networks of low-quality links that the tool counts but Google ignores, then sell links on that site at a premium. That is one of the clearest reasons not to buy anything on the strength of a score alone, and to look instead at whether the site has real readers in your field.

There is a reason these scores exist: Google stopped publishing its own public PageRank figure many years ago, and SEO professionals wanted some way to compare sites. Tool scores fill that gap, but they only see the links the tool's own crawler has found, which is a fraction of the web. A site can have strong local relevance, real reviews and a solid reputation that no link-based score reflects at all.

Example

A florist is offered a guest-post deal on a site with a high authority score. The site publishes articles on every topic, has no real readers and sells links openly. Despite the impressive number, a link there would be irrelevant and risky. A link from the local wedding venue's supplier page, with a modest score, is worth far more.

To judge the offer properly, the florist ignores the score and checks three things herself. Does the site publish anything related to flowers or weddings? Does it appear to have real readers, such as comments, social shares or a mention elsewhere? And does it rank in Google for any searches of its own? A site that fails all three is a link farm, whatever number a tool attaches to it.

Why it matters for your business

Authority scores are useful for quickly comparing sites, spotting link opportunities or tracking a broad trend. They become harmful when treated as a goal, because they push people towards buying links from high-score sites that Google may ignore or penalise. Judge links on relevance and real audience, and judge your SEO on rankings, traffic and enquiries. A rising score is not a result in itself; enquiries, rankings for searches that matter and real referral visits are.

Common mistakes

• Believing Google uses Domain Authority or Domain Rating to rank pages.
• Paying for links mainly because the selling site has a high score.
• Panicking when a score drops after the tool recalculates its model.
• Reporting the score to clients or managers as the main measure of SEO success.

Questions people ask

Does Google use domain authority?

No. Domain Authority is a Moz metric, and similar scores come from Ahrefs, Semrush and other tools. Google has said it does not use these third-party scores. Google evaluates pages and sites with its own signals, including links, but it does not publish a site-wide authority number.

How can I increase my domain authority?

The scores rise mainly when more relevant, trusted sites link to you, which is also what helps real rankings. Earn mentions through real work, partnerships, local press and useful content. Avoid buying links to move the number: the score may rise while your actual search performance does not, or gets worse.

What is a good domain authority score?

There is no absolute good score, because the numbers are relative. Compare yourself with the sites that rank for your searches, not with large national brands. A local business with a modest score can outrank stronger sites when its pages are more relevant and its location and reviews match the search.