Google’s Ranking Factors: Backlink 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 separate 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.
15. 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.
16. “Sponsored Links” Or Other Words Around Link: Words like “sponsors”, “link partners” and “sponsored links” may decrease a link’s value.
17. 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 guestographics.
18. Excessive 301 Redirects to Page: Links coming from 301 redirects dilute some (or even all) PR, according to a Webmaster Help Video.
19. 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.
20. Internal Link Anchor Text: Internal link anchor text is another relevancy signal, although probably weighed differently than backlink anchor text.
21. Link Title Attribution: The link title (the text that appears when you hover over a link) is also used as a weak relevancy signals.
22. 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.
23. Link Location In Content: Links in the beginning of a piece of content carry slightly more weight than links placed at the end of the content.
24. 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.
25. 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.
26. 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.
27. 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.
28. Keyword in Title: Google gives extra love to links on pages that contain your page’s keyword in the title (“Experts linking to experts”.)
29. Positive Link Velocity: A site with positive link velocity usually gets a SERP boost.
30. Negative Link Velocity: Negative link velocity can significantly reduce rankings as it’s a signal of decreasing popularity.
31. 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.
32. 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.
33. 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.
34. Co-Occurrences: The words that tend to appear around your backlinks helps tell Google what that page is about.
35. Backlink Age: According to a Google patent, older links have more ranking power than newly minted backlinks.
36. 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.
37. Natural Link Profile: A site with a “natural” link profile is going to rank highly and be more durable to updates.
38. Reciprocal Links: Google’s Link Schemes page lists “Excessive link exchanging” as a link scheme to avoid.
39. 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.
40. 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.
41. 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 microformatting have a higher SERP CTR:
42. DMOZ Listed: Many believe that Google gives DMOZ listed sites a little extra trust.
43. TrustRank of Linking Site: The trustworthiness of the site linking to you determines how much “TrustRank” gets passed onto you.
44. 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.
45. Forum Profile Links: Because of industrial-level spamming, Google may significantly devalue links from forum profiles.
46. Word Count of Linking Content: A link from a 1000-word post is more valuable than a link inside of a 25-word snippet.
47. 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.
48. Sitewide Links: Matt Cutts has confirmed that sitewide links are “compressed” to count as a single link.