Link Building and Backlinks

Link building is the practice of earning hyperlinks from other websites to your own. A backlink acts as an editorial endorsement: a signal that another site considered your content worth referencing. Google has treated backlinks as a ranking signal since its inception, and they remain one of the most powerful levers available in competitive SEO.

Why do links still matter?

Google’s original PageRank algorithm was built on the premise that a page linked to by many other pages is likely more valuable than one that isn’t. Decades of algorithm updates have made that calculus far more nuanced, but the underlying principle holds.

Links transfer authority, establish topical relevance, and signal that a domain is recognised within its field. A single high-quality link from a relevant, authoritative publication can move rankings more than dozens of low-quality directory submissions. The gap between a good link and a bad one is enormous.

How much weight they carry is contested, and worth seeing plainly rather than assuming. Google’s own position has moved. In 2016, search quality strategist Andrey Lipattsev named links as one of Google’s top three ranking factors. By 2023, Gary Illyes was telling Pubcon Pro the opposite, saying links had not been a top-three factor for some time and that people overestimate their importance: “Links are important, but not as important as people think.”¹ Duy Nguyen of Google’s search quality team put it similarly: “backlinks as a signal has a lot less significant impact compared to when Google Search first started out many years ago. We have robust ranking signals, hundreds of them.”¹

Google speaks for Google, and a self-report is not independent evidence. Practitioners competing on link-heavy commercial queries frequently read their own data differently, and Google has an obvious interest in discouraging link acquisition. Both things can be held at once: links remain a signal worth investing in, and the claim that they are Google’s most heavily weighted signal is not one Google supports.

What makes a link valuable?

Several factors determine a link’s value:

Relevance. A link from a site in your niche or covering your topic is worth more than one from an unrelated domain. Google evaluates topical context: both the linking domain’s focus and the specific page the link sits on.

Authority. The strength of the linking domain matters. Links from established, frequently cited publications transfer more authority than links from new or low-traffic sites. Domain Rating (Ahrefs) and Domain Authority (Moz) are imperfect but useful proxies.

Placement. Editorial links inside body content carry more weight than footer links, sidebar widgets, or links in boilerplate sections. A link a human editor chose to include is the kind Google trusts most.

Anchor text. The clickable text of a link sends a relevance signal. Descriptive, natural anchor text is valuable. Exact-match keyword anchors pointing to the same page in volume look manipulative and can trigger algorithmic or manual penalties.

Uniqueness. A link from a domain that hasn’t linked to you before carries more weight than additional links from the same domain.

Dofollow vs nofollow. Standard links pass authority. Links marked rel="nofollow", rel="ugc", or rel="sponsored" are treated as hints to Google about the nature of the link and generally do not pass the same equity. High-traffic nofollow links from major publications still drive referral visits and build brand visibility.

Link acquisition strategies

Content-led acquisition (link earning)

The most durable links come from content people want to reference. Original research, industry surveys, data-driven studies, and definitive reference resources attract editorial citations because they provide something others can’t easily replicate. This requires upfront investment but builds a compounding asset.

Digital PR

Proactively pitching stories, data, or expert commentary to journalists and publications earns editorial links from high-authority news and media domains. Digital PR links tend to be among the most valuable available: the same publications that dominate traditional media metrics also dominate link equity transfer.

Guest posting

Guest posting means writing for another site in your field in exchange for a link. It stays effective when the article genuinely serves the host’s audience, and becomes a link scheme when the primary purpose is the link rather than the reader.

Prospecting-led acquisition

The remaining approaches share a shape: find a site that has already demonstrated it will link to something like yours, then give it a specific reason to link to you instead. Broken link building offers your page as a replacement for a dead outbound link. Unlinked mention reclamation turns an existing reference into a hyperlink. Competitor backlink analysis works backwards from the domains already linking to your rivals. All three are prospecting methods rather than distinct strategies, and link prospecting and outreach covers them in full, along with qualifying prospects and writing the outreach that converts them.

Do backlinks help AI search visibility?

Yes, but indirectly, and the indirect route is better evidenced than the direct one.

Measured on their own, links correlate poorly. Ahrefs’ December 2025 analysis of 75,000 brands put backlinks at roughly 0.19 to 0.25 and Domain Rating at 0.27 to 0.33, against 0.664 to 0.709 for branded web mentions.² Both are Spearman coefficients, which describe how closely two rankings agree rather than how much of one thing causes another.

Semrush’s October 2025 study of 1,000 domains disagrees, putting its Authority Score against AI mentions at 0.57 Spearman, or 0.65 on Pearson.³ Some of that gap is an artefact of what is being measured. Authority Score is not a link-only metric: Semrush document its inputs as link power, the scored domain’s own organic traffic, and spam factors,⁴ and the traffic component is derived from the domain’s keyword positions. It therefore carries a ranking signal that Ahrefs’ link-only Domain Rating does not, which plausibly accounts for much of the difference. The direct question is unsettled, which is not the same as being answered in the negative.

Two indirect mechanisms are firmer than either correlation.

The link graph decides what gets crawled into the training corpus. Common Crawl computes PageRank and Harmonic Centrality across billions of links and uses them to set crawl priority: “CCBot has been using these metrics to guide its crawling choices”, and sites with higher Harmonic Centrality “are crawled more frequently”.⁵ Common Crawl is the raw material most LLM pre-training is built from. Mozilla’s review of 47 text-generation models published between 2019 and October 2023 found at least 64% used a filtered version of it.⁶ Two things stop this being a strategy: Common Crawl is describing the value of its own data, and appearing in a training corpus is not the same as being cited at inference. The Mozilla figure is also historical, and says nothing about models trained since 2023.

Rankings feed retrieval. AI answers draw on pages that already rank, so anything that lifts rankings improves the odds of entering the source pool. The effect is real but partial. Ahrefs found 37.9% of AI Overview citations came from URLs appearing in the first ten blocks of the results page.⁷ Ahrefs counts ads, featured snippets and other features as blocks, so this is not the same as the top ten organic results, and the majority of citations still come from outside them.

One finding cuts across the disagreement. Semrush found nofollow links correlate with AI mentions almost identically to followed ones: 0.509 against 0.504 on Spearman, and 0.340 against 0.334 on Pearson.³ If passed authority were the mechanism, followed links should pull clearly ahead. They do not, which points at the mention doing the work rather than the equity it carries. That reconciles the two studies, and the practical implication is the same either way: a campaign built to earn coverage serves both surfaces, while a campaign built to place links serves only one. Digital PR and brand mentions cover the coverage side.

What to avoid

Buying links. Google’s guidelines prohibit paid links that pass PageRank. The usual consequence is not a penalty but nullification: SpamBrain, Google’s “AI-based spam-prevention system”, detects both sites buying links and sites passing them, and Google’s aim is to “nullify these unnatural links at scale”, with the result that “ranking may change as spammy links are neutralized and any credit passed by these unnatural links are lost”.⁸ The money buys a link that stops counting rather than a demotion. Manual actions are a separate and rarer outcome for the clearest cases, and those do suppress. Either way the risk-to-reward ratio has deteriorated as Google’s detection has improved.

Link exchanges. “Link to me, I’ll link to you” schemes are explicitly called out in Google’s spam policies. Occasional reciprocal links from genuinely relevant partners are normal; systematic exchanges are not.

Private blog networks (PBNs). Networks of sites created specifically to pass links violate Google’s guidelines. Detection and devaluation of PBN links is ongoing and improving.

Low-quality directories. Submissions to generic, low-quality aggregator sites provide no meaningful authority and may dilute your link profile.

How do you measure link building success?

Track progress through a combination of:

• New referring domains (growth in unique linking sites, not total link count)
• Link quality (Domain Rating or Domain Authority of acquiring domains)
• Organic ranking movement for target pages
• Organic traffic growth to link-targeted pages over time

Links take time to influence rankings: weeks to months, depending on crawl frequency and the authority of the linking domain. Short-term attribution is unreliable; measure link building impact over quarters, not days.

The same compounding logic applies to both international link building and local link building in each target market. Each geography requires its own link profile built from scratch, following an independent SEO timeline. Link prospecting and outreach are the discovery mechanisms in every context. Black-hat SEO techniques, including paid links and link schemes, carry the same penalty risk across all markets and should be avoided in favour of white-hat SEO acquisition that earns links through genuine editorial value.

Footnotes

1. Links are not a top 3 Google Search ranking factor, says Gary Illyes — Search Engine Land, 25 September 2023. Also records Duy Nguyen’s remarks from a Google SEO Office Hours, and the 2016 Lipattsev statement the position moved away from. ↩ ↩²

2. Top Brand Visibility Factors in ChatGPT, AI Mode, and AI Overviews (75k Brands Studied) — Ahrefs. Spearman correlations, December 2025. The authors explicitly caution that correlation is not causation. ↩

3. Do Backlinks Still Matter in AI Search? Insights from 1,000 Domains — Semrush. 1,000 randomly selected domains across ChatGPT, ChatGPT Search, Gemini, AI Overviews and Perplexity, October 2025. Pearson and Spearman correlations. ↩ ↩²

4. What is Authority Score? — Semrush. Documents the three facets: link power, organic traffic, and spam factors. ↩

5. How SEOs Are Using Common Crawl’s Web Graph Data for AI Ranking Signals — Common Crawl. Common Crawl describing its own Web Graph release. ↩

6. Training Data for the Price of a Sandwich: Common Crawl’s Impact on Generative AI — Mozilla Foundation. Review of 47 text-generation LLMs published between 2019 and October 2023. ↩

7. Update: 38% of AI Overview Citations Pull From The Top 10 — Ahrefs. 863,000 keyword SERPs and 4 million AI Overview URLs, March 2026. ↩

8. December 2022 link spam update — Google Search Central Blog ↩