What Are Backlinks? SEO Definition, Types & How to Earn Them

A backlink is an inbound hyperlink from one website to another — when Site B links to Site A, that link is a backlink for Site A. In SEO, backlinks are also called inbound links, external links, or simply "links." Google's original PageRank algorithm treated links as votes: if reputable sites link to your page, that page is probably worth surfacing in search results. Links remain one of the strongest off-page ranking signals more than two decades later.

Why Backlinks Matter for SEO

Google uses backlinks to understand two things: whether a page is worth trusting, and what a page is about. A high-authority site in your industry linking to your article sends a signal that other experts in the space consider your content valuable. The anchor text of that link (the clickable words) tells Google the topic context — "best robots.txt checker" as anchor text signals something very different from "click here."

Pages with more high-quality backlinks consistently rank higher for competitive queries than pages without them, all else being equal. For most content-focused sites, building a backlink profile is the hardest and slowest part of SEO — which is exactly why it is so valuable as a competitive moat.

Dofollow vs. Nofollow

By default, most links pass PageRank (often called "link equity" or "link juice"). A rel="nofollow" attribute tells Google not to pass ranking credit through that link. Sponsored content uses rel="sponsored"; user-generated links often carry rel="ugc". Since 2019, Google treats all three as hints rather than hard directives — it may still choose to count a nofollow link as a signal in some cases.

Nofollow links from major publications still drive referral traffic, brand visibility, and indirect SEO benefits. When a Forbes article links to your research with nofollow, other editors and writers see it — that visibility often produces organic dofollow links later. Do not dismiss nofollow links from high-traffic, authoritative sources.

What Makes a Backlink Valuable

Not all backlinks carry equal weight. These factors determine how much a link moves your rankings:

• Relevance — A link from a DR 30 site in your exact industry usually outperforms a link from a DR 70 general news site on an unrelated topic. Google evaluates topical context.
• Placement — Editorial links within the main body content of an article outperform footer links, sidebar links, or links in site-wide navigation.
• Unique referring domains — 100 links from 100 different domains is far more valuable than 100 links from one domain. Diversification signals genuine interest from multiple sources.
• Anchor text — Descriptive anchors help Google understand what your linked page is about. Over-optimized exact-match anchors across many links look unnatural and can trigger spam filters.
• Authority of the linking page — A link from a page with many of its own high-quality backlinks passes more equity than a link from a page with none.

Types of Backlinks

Understanding the different types helps you focus your acquisition efforts on the links that actually move rankings:

• Editorial links — Earned naturally when other sites cite your content as a source. The most valuable type because they represent genuine third-party endorsement.
• Guest post links — Links in articles you write for other publications. Still valid when done on relevant, high-quality sites with real audiences — not on link farms.
• Resource page links — Links from pages that curate useful tools or guides in a niche. Reachable through targeted outreach.
• Broken link building — Finding dead links on authoritative sites and suggesting your content as a replacement. One of the most conversion-efficient outreach tactics.
• Digital PR links — Coverage earned through original research, data studies, or newsworthy content that journalists and bloggers cite.

How Many Backlinks Do You Need?

The honest answer: it depends entirely on competition. The right benchmark is not an absolute number — it is the link profile of the pages currently ranking for your target keyword. If the top three results for "best project management software" each have 200+ referring domains pointing to that specific URL, ranking without a comparable profile is very difficult. If your target keyword shows results from sites with 10–30 referring domains per URL, that gap is closeable.

Use Ahrefs, Semrush, or Moz to check URL-level referring domains for your top competitors — not just sitewide DR. The URL that ranks is what matters, not the domain's overall authority.

Link Types That Usually Fail

Paid link schemes, private blog networks (PBNs), mass directory submissions, and automated guest post farms produce temporary gains followed by manual actions or algorithmic devaluation. Google's spam policies explicitly penalize link schemes designed to manipulate PageRank. If a link offer sounds too easy — "DR 60+ guest posts for $50" — it is a PBN, a hacked site, or a network Google already discounts.

Earning links through original research, useful free tools, expert commentary, and genuine relationships scales slower but compounds over time without the risk of a penalty that wipes out years of work overnight. That is the approach covered in depth in our link building guide, which walks through digital PR, broken link building, and outreach templates that actually get responses.

How to Check Your Backlinks

Google Search Console shows some of your backlinks under the Links report — not all of them, but a useful sample. For a fuller picture, Ahrefs, Semrush, and Moz each maintain their own link indexes. No single tool catches every link. Using two tools together gives a more complete view. For URL indexing and getting new pages discovered faster, see Indexaro, a dedicated Google index submission tool.