Domain Authority is a score (on a 100-point scale) developed by Moz that predicts how well a website will rank on search engines. Use Domain Authority when comparing one site to another or tracking the “strength” of your website over time. We calculate this metric by combining all of our other link metrics—linking root domains, number of total links, MozRank, MozTrust, etc.—into a single score.
To determine Domain Authority, Moz employs machine learning against Google’s algorithm to best model how search engine results are generated. Over 40 signals are included in this calculation. This means your website’s Domain Authority score will often fluctuate. For this reason, it’s best to use Domain Authority as a competitive metric against other sites as opposed to a historic measure of your internal SEO efforts.
It’s best to use Page Authority (PA) and Domain Authority (DA) as comparative metrics when doing research in the search results and determining which sites/pages may have more powerful, important, link profiles than others.
Domain Authority Factors:
1. Linking Domain Age: Backlinks from aged domains may be more powerful than new domains.
2. # of Linking Root Domains: The number of referring domains is one of the most important ranking factors in Google’s algorithm, as you can see from this chart from Moz (bottom axis is SERP position):
3. # of Links from Separate C-Class IPs: Links from seperate class-c IP addresses suggest a wider breadth of sites linking to you.
4. # of Linking Pages: The total number of linking pages — even if some are on the same domain — is a ranking factor.
5. Alt Tag (for Image Links): Alt text is an image’s version of anchor text.
6. Links from .edu or .gov Domains: Matt Cutts has stated that TLD doesn’t factor into a site’s importance. However, that doesn’t stop SEOs from thinking that there’s a special place in the algo for .gov and .edu TLDs.
7. Authority of Linking Page: The authority (PageRank) of the referring page is an extremely important ranking factor.
8. Authority of Linking Domain: The referring domain’s authority may play an independent role in a link’s importance (ie. a PR2 page link from a site with a homepage PR3 may be worth less than a PR2 page link from PR8 Yale.edu).
9. Links From Competitors: Links from other pages ranking in the same SERP may be more valuable for a page’s rank for that particular keyword.
10. Social Shares of Referring Page: The amount of page-level social shares may influence the link’s value.
11. Links from Bad Neighborhoods: Links from “bad neighborhoods” may hurt your site.
12. Guest Posts: Although guest posting can be part of a white hat SEO campaign, links coming from guest posts — especially in an author bio area — may not be as valuable as a contextual link on the same page.
13. Links to Homepage Domain that Page Sits On: Links to a referring page’s homepage may play special importance in evaluating a site’s — and therefore a link’s — weight.
14. Nofollow Links: One of the most controversial topics in SEO. Google’s official word on the matter is: “In general, we don’t follow them.”
Which suggests that they do…at least in certain cases. Having a certain % of nofollow links may also indicate a natural vs. unnatural link profile.
16. Diversity of Link Types: Having an unnaturally large percentage of your links come from a single source (ie. forum profiles, blog comments) may be a sign of webspam. On the other hand, links from diverse sources is a sign of a natural link profile.
17. “Sponsored Links” Or Other Words Around Link: Words like “sponsors”, “link partners” and “sponsored links” may decrease a link’s value.
18. Contextual Links: Links embedded inside a page’s content are considered more powerful than links on an empty page or found elsewhere on the page.
A good example of contextual links are backlinks from geographics.
19. Excessive 301 Redirects to Page: Links coming from 301 redirects dilute some (or even all) PR.
20. Backlink Anchor Text: As noted in this description of Google’s original algorithm:
“First, anchors often provide more accurate descriptions of web pages than the pages themselves.”
Obviously, anchor text is less important than before (and likely a webspam signal). But it still sends a strong relevancy signal in small doses.
21. Internal Link Anchor Text: Internal link anchor text is another relevancy signal, although probably weighed differently than backlink anchor text.
22. Link Title Attribution: The link title (the text that appears when you hover over a link) is also used as a weak relevancy signals.
23. Country TLD of Referring Domain: Getting links from country-specific top level domain extensions (.de, .cn, .co.uk) may help you rank better in that country.
24. Link Location In Content: Links in the beginning of a piece of content carry slight more weight than links placed at the end of the content.
25. Link Location on Page: Where a link appears on a page is important. Generally, links embedded in a page’s content are more powerful than links in the footer or sidebar area.
26. Linking Domain Relevancy: A link from site in a similar niche is significantly more powerful than a link from a completely unrelated site. That’s why any effective SEO strategy today focuses on obtaining relevant links.
27. Page Level Relevancy: The Hilltop Algorithm states that link from a page that’s closely tied to page’s content is more powerful than a link from an unrelated page.
28. Text Around Link Sentiment: Google has probably figured out whether or not a link to your site is a recommendation or part of a negative review. Links with positive sentiments around them likely carry more weight.
29. Keyword in Title: Google gives extra love to links on pages that contain your page’s keyword in the title (“Experts linking to experts”.)
30. Positive Link Velocity: A site with positive link velocity usually gets a SERP boost.
32. Negative Link Velocity: Negative link velocity can significantly reduce rankings as it’s a signal of decreasing popularity.
33. Links from “Hub” Pages: Aaron Wall claims that getting links from pages that are considered top resources (or hubs) on a certain topic are given special treatment.
34. Link from Authority Sites: A link from a site considered an “authority site” likely pass more juice than a link from a small, microniche site.
35. Linked to as Wikipedia Source: Although the links are nofollow, many think that getting a link from Wikipedia gives you a little added trust and authority in the eyes of search engines.
36. Co-Occurrences: The words that tend to appear around your backlinks helps tell Google what that page is about.
37. Backlink Age: According to a Google patent, older links have more ranking power than newly minted backlinks.
38. Links from Real Sites vs. Splogs: Due to the proliferation of blog networks, Google probably gives more weight to links coming from “real sites” than from fake blogs. They likely use brand and user-interaction signals to distinguish between the two.
39. Natural Link Profile: A site with a “natural” link profile is going to rank highly and be more durable to updates.
“Any links intended to manipulate PageRank or a site’s ranking in Google search results may be considered part of a link scheme and a violation of Google’s Webmaster Guidelines. This includes any behavior that manipulates links to your site or outgoing links from your site.”
40. Reciprocal Links: Google’s Link Schemes page lists “Excessive link exchanging” as a link scheme to avoid.
41. User-Generated Content Links: Google is able to identify links generated from UGC vs. the actual site owner. For example, they know that a link from the official WordPress.com blog at en.blog.wordpress.com is very different than a link from besttoasterreviews.wordpress.com.
42. Links from 301: Links from 301 redirects may lose a little bit of juice compared to a direct link. However, Matt Cutts says that a 301 is similar to a direct link.
43. Schema.org Microformats: Pages that support microformats may rank above pages without it. This may be a direct boost or the fact that pages with micro-formatting have a higher SERP CTR:
44. DMOZ Listed: Many believe that Google gives DMOZ listed sites a little extra trust.
45. TrustRank of Linking Site: The trustworthiness of the site linking to you determines how much “TrustRank” gets passed onto you.
46. Number of Outbound Links on Page: PageRank is finite. A link on a page with hundreds of OBLs passes less PR than a page with only a few OBLs.
47. Forum Profile Links: Because of industrial-level spamming, Google may significantly devalue links from forum profiles.
48. Word Count of Linking Content: A link from a 1000-word post is more valuable than a link inside of a 25-word snippet.
49. Quality of Linking Content: Links from poorly written or spun content don’t pass as much value as links from well-written, multimedia-enhanced content.
50. Sitewide Links: Matt Cutts has confirmed that sitewide links are “compressed” to count as a single link.