Domain Authority is the number people quote when they want to sound sure about a website. "It's a DA 50" ends more link-buying conversations than any other phrase in SEO. The trouble is that most people using it can't say what it measures, who calculates it, or why a DA 50 site can have less real traffic than a DA 20 site.
This guide explains what Moz Domain Authority, Ahrefs Domain Rating and Semrush Authority Score actually tell you, why Google uses none of them, how each one gets gamed, and what to check alongside them before you spend money on a placement or judge your own site's progress.
What Domain Authority actually is
Domain Authority (DA) is a score from Moz that predicts how likely a domain is to rank compared with other domains. It runs from 0 to 100 and is built mainly from Moz's own index of links: how many distinct domains link to a site, how strong those linking domains are, and how the profile compares with sites that rank well. Three properties matter more than the formula.
- It is third-party. Moz calculates DA from its own crawl. Google has no involvement and no reason to agree with it.
- It is logarithmic. Moving from DA 10 to 20 is far easier than moving from 60 to 70. Each step higher requires disproportionately more link equity.
- It is comparative, not absolute. DA ranks sites against each other. Your score can drop without you losing a single link, simply because Moz recalculated, expanded its index, or the sites around you gained ground.
That last point trips people up. A DA drop is not a penalty and a DA gain is not a reward from Google. It's a movement on a scoreboard maintained by one company.
DR and Authority Score: the other two numbers
Ahrefs Domain Rating (DR)
Ahrefs' DR is also 0 to 100 and logarithmic, but it measures one thing: the strength of a site's backlink profile, based on how many unique domains link to it and how strong those domains are. DR ignores traffic entirely. That makes it a clean link-strength signal and also the easiest of the three to inflate, because links are the only input.
Semrush Authority Score (AS)
Semrush's Authority Score blends link data with organic traffic estimates and spam signals. A site with a large backlink profile but no organic visibility tends to score lower in AS than in DR, which is why buyers who have been burned by link farms often prefer it. The cost is that AS is harder to interpret: a change can come from links, traffic, or Semrush adjusting how it weights them.
| Metric | Provider | Main inputs | Ignores | Best used for |
|---|---|---|---|---|
| Domain Authority (DA) | Moz | Linking domains, link quality, fit to ranking data | Traffic, content quality | Comparing sites in the same niche at a glance |
| Domain Rating (DR) | Ahrefs | Number and strength of unique linking domains | Traffic, spam, relevance | Judging raw link equity of a domain |
| Authority Score (AS) | Semrush | Backlink profile, organic traffic, spam indicators | Topical relevance to you | Filtering out link-inflated sites with no real audience |
Because the three tools crawl different link indexes and weight things differently, the same site can be DA 45, DR 62 and AS 30. They're three opinions from three datasets, not one truth.
Why Google doesn't use any of them
Google has said repeatedly that it has no "domain authority" metric of the kind SEO tools publish. Its systems evaluate individual pages and links, using signals none of these tools can see, including whether a link looks paid or manipulative under its link spam policies.
So when a DA 70 site links to you, Google doesn't see "70." It sees a specific page, its relevance to yours, the anchor text, where the link sits, and the history of that site's outbound links. A DA 70 site that sells hundreds of sponsored posts a month with generic anchors passes far less than the number implies.
An authority score describes a site's past ability to attract links. It says nothing about whether a link from that site will help you rank.
How authority scores get gamed
Because DA and DR are built from links, links are how they're inflated. The common patterns:
- Bulk low-quality links. Thousands of links from expired domains, forum profiles and directory spam push DR up quickly. Traffic stays flat.
- Private blog networks. A ring of sites linking to each other, all with tidy mid-range scores and no organic keywords worth mentioning.
- Redirected expired domains. Someone buys a dead domain with a strong old link profile and redirects it to a new site. The score transfers; the relevance and audience don't.
- Link selling at scale. The site keeps a decent score but its outbound profile is a wall of casino, CBD and payday-loan anchors.
None of these show up in the headline number. All of them show up in the checks below.
What to check alongside the score
Treat DA, DR and AS as a first filter, then verify with data that's harder to fake.
- Organic traffic. Pull the site's estimated organic visits in Ahrefs or Semrush. A site with authority and no traffic is either brand-new, penalized, or built from links alone.
- Traffic trend. Look at the twelve-month graph, not the current number. A cliff-edge drop usually means an algorithm update hit the site, and a link from it is worth less.
- Spam score. Moz's spam score and Semrush's toxicity indicators aren't perfect, but a high value combined with a high DA is a red flag, not a bargain.
- Indexed pages. Run a site: search. Thousands of pages with only a handful indexed means Google isn't interested.
- Topical relevance. Does the site rank for keywords in your niche, or would your post sit next to unrelated content?
- Outbound link profile. Open five recent posts. If every one carries a commercial do-follow link to a different client, the site is a link seller first.
How buyers should use DA, DR and AS when choosing sites
Use the scores to set a floor, not to pick winners. A practical workflow looks like this:
- Set a minimum on one metric. Many buyers use DR because it's widely available, then cross-check with AS to catch traffic-free sites.
- Filter for organic traffic above a threshold that matters to you and a flat or rising trend.
- Filter for language, country and topical fit. A relevant DA 30 site in your market beats a general DA 60 site in another one.
- Check the price against the site's real reach, not its score. Sellers price by DA because buyers pay by DA; you don't have to.
On BacklinkCAT, listings show Moz DA, Ahrefs DR, Semrush Authority Score and estimated traffic side by side with spam score, language, country and link type, so you can filter on the combination rather than one number. The "ownership verified" badge and automatic site health checks also catch fake listings and sites that quietly dropped out of the index.
For a deeper look at judging individual placements, see our guide to building high-quality backlinks.
How publishers can improve their score honestly
Buyers filter on these numbers, so they affect your income. The honest ways to move them are slow but durable.
- Earn links to inner pages, not just the homepage. Guides, original data and tools attract links naturally and spread authority across the site.
- Keep the outbound profile clean. Cap sponsored posts, decline off-topic niches, and use rel="sponsored" where a link is paid. A site that looks like a publication keeps its score; a site that looks like a billboard loses it.
- Do some digital PR of your own. A single link from a national outlet does more for DA and DR than fifty reciprocal links. Our digital PR guide covers how.
- Don't buy links to raise your score. It works on the number and fails on everything else. Experienced buyers will see the traffic gap and pass.
Key takeaways
- DA, DR and AS are third-party, 0 to 100, logarithmic estimates from three different link indexes. None is a Google ranking factor.
- Links inflate scores; traffic, trend, indexation and relevance reveal whether the score is real.
- Buyers should use the metrics as a floor and decide on traffic and fit. Publishers should grow them by earning links and keeping outbound links clean.
