What Are Backlinks?
9 min read
Backlinks (also called inbound links or external links) are hyperlinks on one website that point to a webpage on a different domain. Since Google founders Larry Page and Sergey Brin introduced the PageRank algorithm (US Patent US6285999B1) in 1998, search engines have treated editorial backlinks as third-party peer-review citations: evaluating the linking page’s PageRank authority, topical relevance, seed-site distance, and contextual anchor text to determine which pages deserve to rank #1 on competitive commercial queries.
How Google Evaluates Backlinks: From Original PageRank to the "Reasonable Surfer" Model
In early search engines (1994-1997), rankings were based almost entirely on how many times a keyword appeared on a page, making it trivial for spammers to rank low-quality sites. In 1998, Stanford PhD candidates Larry Page and Sergey Brin solved this by modeling the web after academic citation graphs: a research paper is considered authoritative not because it claims to be important, but because other respected papers cite it.
Over the last 28 years, Google’s link evaluation system evolved through three major architectural milestones:
- Original PageRank (US Patent US6285999B1, 1998): Treated every link on a page as an equal mathematical vote, dividing a page’s PageRank score equally among all outgoing links on that URL.
- The "Reasonable Surfer" Patent (US Patent US7716225B1, 2004/2010): Replaced equal link weighting with a probability model based on how likely a real human is to click the link. A contextual link placed in the first two paragraphs (above the fold) of a relevant article passes significantly more PageRank than a tiny link buried in a footer or author bio box!
- Seed-Site Distance & Link-Based Trust (US Patent US9165040B1 & SpamBrain): Rather than trusting easily manipulated link networks, Google calculates link authority starting from a curated set of high-trust seed sites (major news outlets, .edu universities, .gov institutions, and category leaders). The closer your domain is in link hops to verified seed sites, the stronger your authority.
Anatomy of a High-Impact Backlink vs. a Worthless Toxic Link
In modern SEO, 1 contextual backlink from a trusted, topically relevant software publication outweighs 500 low-quality directory or link-farm links. Here is how Google’s algorithms score link quality:
| Link Evaluation Factor | High-Impact Editorial Backlink (Passes Strong Equity) | Low-Quality / Spam Backlink (Ignored by SpamBrain) |
|---|---|---|
| 1. Topical & Entity Relevance | A B2B FinTech or SaaS engineering site linking to your SaaS API or comparison guide. | A generic "General News / Casino / Lifestyle" guest-post farm linking to a B2B software page. |
| 2. Real Organic Traffic & Rankings | The linking domain ranks for thousands of real keywords in Google and receives human traffic. | Inflated DR 70 domain with 0 organic traffic in Ahrefs (manipulated redirect spam). |
| 3. DOM Placement (Reasonable Surfer) | Editorial in-content link surrounded by topically relevant sentences in the main <article> body. |
Sitewide footer link, blogroll widget, or unmoderated forum comment signature. |
| 4. Anchor Text & Annotation Window | Natural branded, compound, or partial-match anchor surrounded by descriptive topic context. | Forced commercial exact-match anchor repeated across dozens of low-tier sites (triggers Penguin). |
| 5. HTML Link Attribute | Clean standard <a href="..."> tag (Dofollow) on an indexable HTTP 200 OK page. |
Tagged with rel="nofollow", rel="sponsored", or placed on a noindex page. |
Understanding HTML Link Attributes: Dofollow vs. Nofollow, Sponsored & UGC
In September 2019, Google Search Central updated its link attribute system from a single binary nofollow directive into three granular link hints:
- Standard Dofollow Link (
<a href="https://example.com">): Norelblocking attribute is needed; by default, standard HTML links pass full PageRank and anchor text signals. rel="nofollow"(Introduced 2005, Updated to a "Hint" in 2019): Tells Google not to associate your site with, or pass PageRank to, the linked page. Since 2019, Google treatsnofollowas a hint, meaning Google may still choose to credit natural editorialnofollowlinks from major publications (like Forbes, Wikipedia, or NYT).rel="sponsored": Explicitly required by Google Search Essentials for paid advertisements, paid sponsorships, or compensated placements.rel="ugc"(User-Generated Content): Recommended for links created by users inside community forums, Reddit threads, and blog comment sections.
How B2B SaaS Companies Earn High-Authority Backlinks That Move Revenue Pages
The 4 Highest-ROI White-Hat Link Acquisition Channels for SaaS
1. Original First-Party Data & Benchmark Studies: Aggregate anonymized usage data from your software platform into an annual state-of-the-industry report. Journalists and bloggers cite statistics constantly, turning your study into a passive backlink magnet.
2. Strategic B2B SaaS Editorial Link Building: Collaborate with non-competing, high-DR SaaS brands (e.g., CRM, HRTech, DevTools, and Martech companies sharing the same ICP) to earn contextual in-content links pointing directly to your BOFU guides and product hubs.
3. Free Interactive Micro-Tools & Calculators: Build a free, ungated engineering utility, ROI calculator, or schema generator in your subfolder. Tools earn 3x to 5x more natural referring domains than standard blog posts.
4. "Surround Sound" Listicle & Integration Directory Inclusion: Get added to existing high-ranking third-party "Best [Category] Software" articles and partner app marketplaces, which simultaneously pass referral traffic, backlink equity, and LLM training citations!
Frequently Asked Questions
Do backlinks still matter for Google rankings in 2026 after AI and Helpful Content updates?
Yes, immensely: especially for competitive commercial B2B keywords! While Google can rank a low-competition long-tail article based on on-page semantic relevance alone, when 20 SaaS companies all publish comprehensive pages targeting "best enterprise CRM software" or "HIPAA compliant telehealth platform", authoritative backlinks and Navboost user signals remain the primary tie-breakers.
What is the difference between Referring Domains and Total Backlinks?
Total Backlinks counts every individual hyperlink pointing to your site (even if 500 links come from the same single website). Referring Domains counts the number of unique, independent websites linking to you. Earning 1 backlink each from 50 different authoritative Referring Domains is vastly more powerful than getting 500 backlinks from 1 website.
Do backlinks help with Answer Engine Optimization (AEO) in ChatGPT and Perplexity?
Yes, in two direct ways: first, live RAG search engines (ChatGPT Search, Perplexity, Google AI Overviews) retrieve their grounding sources from pages that rank at the top of Google and Bing: which requires strong backlink authority. Second, editorial backlinks on trusted third-party domains create the entity co-occurrence patterns LLMs rely on to recommend brands.
Should I regularly disavow spammy scraper backlinks in Google Search Console?
Usually no. Google’s John Mueller and Gary Illyes have confirmed that Google’s SpamBrain AI automatically ignores random scraper, directory, and auto-generated bot links pointing to your site. You should only use the Disavow Tool if you have received a Manual Action for unnatural links or if a past agency actively built toxic paid PBN links.