How Backlinks Work
Search engines like Google use backlinks to assess a page's authority and relevance. The logic: if reputable sites link to your content, your content is probably valuable. This principle dates back to Google's original PageRank algorithm, which treated links as citations in academic papers.
Not all backlinks are equal. A link from The New York Times carries more weight than a link from a brand-new blog. Search engines evaluate:
Source authority: Links from high domain authority sites pass more value
Relevance: A link from a site in your industry matters more than one from an unrelated niche
Anchor text: The clickable text of the link signals what the target page is about
Link placement: Editorial links within content are stronger than footer or sidebar links
Follow vs. nofollow: rel="nofollow" tells search engines not to pass ranking credit
Types of Backlinks
Editorial links are earned naturally when someone references your content because it's useful. These are the most valuable—and the hardest to get.
Guest post links come from contributing content to other sites. Quality varies widely; links from reputable publications help, while links from low-quality "guest post farms" can hurt.
Directory links are from business directories, industry listings, or resource pages. Legitimate directories (like industry associations) are fine; spammy directories should be avoided.
Social links from platforms like Twitter or LinkedIn typically use nofollow and don't directly impact rankings, but they can drive traffic that leads to natural backlinks.
Why Backlinks Matter for Domain Buyers
When evaluating expired domains or aftermarket domains, the backlink profile is often the primary value driver. A domain with quality backlinks from relevant, authoritative sites can give your project a significant SEO head start.
Key metrics to assess:
Number of referring domains: Unique sites linking to the domain (more important than total link count)
Domain authority of linking sites: Are reputable sites linking, or just spam?
Anchor text distribution: Natural profiles have varied anchor text; over-optimized profiles suggest manipulation
Link relevance: Do the backlinks make sense for your intended use?
You can analyze backlink profiles using tools like Ahrefs, Moz, or Semrush before purchasing. A domain with 500 links from 5 sites is less valuable than one with 50 links from 50 different quality sites.
Backlinks and Expired Domains
Expired domains with strong backlink profiles are particularly valuable for:
Building new projects: Start with existing authority rather than from zero
301 redirects: Point an expired domain to your main site to transfer some link equity
Content sites: Revive a domain in its original niche to maintain backlink relevance
Be cautious of expired domains with spammy backlink profiles. Previous owners may have engaged in link schemes that resulted in Google penalties. Always audit the backlink profile before purchasing.
How to Earn Backlinks
Quality backlinks come from creating content others want to reference. Effective approaches include:
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Original research: Data, surveys, and studies get cited
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Comprehensive guides: Definitive resources on a topic attract links
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Free tools: Useful tools earn natural links (like a domain name generator)
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Expert commentary: Being quoted in industry publications
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Broken link building: Finding dead links on other sites and offering your content as a replacement
Avoid buying links, participating in link exchanges, or using private blog networks (PBNs). These tactics violate Google's guidelines and risk penalties that can tank your rankings.
Checking Your Backlink Profile
Monitor your backlinks regularly to:
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Identify new links you've earned
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Spot toxic links that could hurt your rankings
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Find link-building opportunities by seeing who links to competitors but not you
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Disavow harmful links through Google Search Console if necessary
Most SEO tools provide backlink analysis. Free options include Google Search Console (limited data) and Ahrefs Webmaster Tools (your own site only).
Frequently Asked Questions
What is a backlink?
A backlink is a link from one website to another. When site A links to site B, that's a backlink for site B. Search engines use backlinks as signals of trust and authority—more quality backlinks generally means better search rankings.
Why are backlinks important for SEO?
Backlinks are one of Google's top ranking factors. They act as votes of confidence—when reputable sites link to your content, search engines interpret this as a signal that your content is valuable and trustworthy, which can improve your rankings.
How many backlinks do I need to rank?
There's no magic number. Quality matters more than quantity. A few backlinks from highly authoritative, relevant sites can outperform hundreds of links from low-quality sources. Focus on earning links from reputable sites in your niche.
What's the difference between dofollow and nofollow links?
Dofollow links (the default) pass ranking credit to the linked page. Nofollow links include a rel="nofollow" attribute that tells search engines not to pass ranking value. Nofollow links can still drive traffic but don't directly boost SEO.
Can bad backlinks hurt my site?
Yes. Links from spammy, irrelevant, or penalized sites can harm your rankings. If you inherit toxic backlinks (common with expired domains) or get hit by negative SEO, you may need to disavow those links through Google Search Console.
How do I check my backlinks?
Use SEO tools like Ahrefs, Moz, Semrush, or Majestic to analyze your backlink profile. Google Search Console also shows some backlinks for free, though with limited data. These tools reveal who's linking to you, anchor text used, and link quality.