Understanding what a backlink is is one of the most important foundations in SEO. Backlinks - links from other websites pointing to yours - have been a central ranking signal since Google’s earliest days, and despite decades of algorithm updates, they remain one of the top three factors determining where your pages appear in search results. If you want to understand why some sites rank effortlessly while others struggle, the answer almost always comes back to the quality and quantity of their backlinks.
TL;DR: Key Takeaways
- A backlink is a link from one website to another. When Site A links to Site B, Site B receives a backlink.
- Backlinks are one of Google’s top 3 ranking factors. They signal to Google that other sites consider your content credible and worth referencing.
- Not all backlinks are equal: links from authoritative, relevant, and trusted sites carry far more weight than links from low-quality sources.
- The most sustainable way to earn backlinks is by creating content worth linking to and promoting it strategically.
- Toxic backlinks (spam, paid link schemes) can harm rankings and should be disavowed.
What Is a Backlink?
A backlink is a hyperlink from one website that points to a page on another website. When a blog post links to your article as a source, you have received a backlink from that blog. When a news site cites your research data and links to it, that is a backlink.
Backlinks are also called inbound links, incoming links, or external links (from the perspective of the linking site). They are a fundamental concept in how search engines evaluate website authority and relevance.
This article is for anyone building or managing an online presence who wants to understand how backlinks work, why they matter for SEO, and what they can do to earn more of them.
When Google’s founders Larry Page and Sergey Brin built the original PageRank algorithm at Stanford in 1998, backlinks were the core signal. The idea was elegant: if many credible websites link to a page, that page is probably valuable. Over 25 years later, backlinks remain one of the most powerful signals in Google’s ranking algorithm.
Why Backlinks Matter for SEO
Backlinks matter for SEO because they function as votes of confidence. Each link from a credible source tells Google: “This page is trustworthy and useful enough that I’m willing to direct my own audience to it.”
Google’s algorithm uses these signals to make ranking decisions. Pages with more high-quality backlinks consistently rank higher than pages with fewer, all else being equal.
According to a large-scale 2023 Ahrefs study analyzing over 1 billion web pages, 66.3% of all pages have zero backlinks pointing to them from external websites. Pages with no backlinks receive almost no organic traffic from Google. The correlation between backlink count and organic traffic is strong and consistent.
Backlinks also influence:
- Crawl frequency: Pages with many inbound links get crawled more often by Googlebot, meaning updates index faster.
- Domain authority: The accumulation of quality backlinks builds a site’s overall authority, lifting rankings for pages across the entire domain.
- Referral traffic: Backlinks from high-traffic sites send visitors directly to your pages, independent of search rankings.
Types of Backlinks
Not all backlinks are created equal. Understanding the different types helps you focus your efforts on links that actually move the needle.
Dofollow vs. Nofollow Backlinks
Dofollow links: Standard links that pass “link equity” (ranking power) to the destination page. When most SEOs talk about building backlinks, they mean dofollow links.
Nofollow links: Links with a rel="nofollow" HTML attribute that tell search engines not to pass ranking credit. Social media links, most comment links, and many user-generated content links are nofollow. They do not directly boost rankings but can drive traffic and contribute to a natural-looking link profile.
In 2019, Google introduced two additional link attributes:
rel="sponsored": For paid or affiliate links.rel="ugc": For user-generated content like comments and forum posts.
Editorial Links
Links earned naturally because another site found your content valuable enough to reference. These are the most powerful backlinks because they represent genuine third-party endorsement.
Guest Post Links
Links earned by writing and publishing content on other websites, with a link back to your site in the body or author bio. High-quality guest posting on relevant, authoritative sites is a legitimate and effective link building strategy. See our guide on SEO guest posting.
Resource Page Links
Links from pages curated specifically to list helpful resources on a topic. Getting listed on a high-authority resource page is a strong backlink source.
Paid Links
Links acquired in exchange for money or other compensation. These violate Google’s Webmaster Guidelines when they are intended to pass PageRank. They carry significant penalty risk if detected.
What Makes a Backlink Valuable?
Not every backlink is worth the same. The value of a backlink depends on several factors:
1. Authority of the Linking Domain
A link from a high-domain-authority site (DA 70+) passes significantly more ranking power than a link from a new or low-authority blog. Tools like Moz, Ahrefs, and SEMrush measure this with their respective domain authority metrics.
2. Relevance of the Linking Site
A link from a site in your industry or niche is worth more than a link from an unrelated site, even if both have similar authority. Google evaluates topical relevance alongside authority.
3. Placement on the Page
Links within the main body of an article pass more link equity than links in footers, sidebars, or author bios. Editorial in-body links are the most valuable placement.
4. Anchor Text
The clickable text of a link (anchor text) gives Google context about the topic of the destination page. Descriptive anchor text with relevant keywords is more informative than generic “click here” anchors. Read our full guide on what is anchor text for best practices.
5. Link Uniqueness
A link from a domain that has never linked to you before is worth more than a second or third link from the same domain. Unique referring domains are the most reliable predictor of ranking strength.
6. Page Traffic
Links from pages that receive significant organic traffic tend to send more referral visitors and carry stronger implicit quality signals.
Good Backlinks vs. Bad Backlinks
Understanding the difference protects your site from penalties:
Good backlinks:
- From relevant, authoritative domains with real editorial standards
- Placed naturally in body content
- Earned because your content is genuinely useful
- Diverse in terms of referring domains and anchor text
Bad backlinks:
- From link farms, PBNs, or sites created solely to sell links
- Spam comment links with keyword-stuffed anchor text
- Links from completely irrelevant niches (a shoe blog linking to a cybersecurity firm)
- Large volumes of links acquired in a short period (unnatural velocity)
If you have bad backlinks in your profile, you can request removal from webmasters or use Google’s Disavow Tool. See our guide on how to disavow links for instructions.
How to Check Your Backlinks
Several tools let you monitor your backlink profile:
Google Search Console (Free): The Links report shows your top linking sites and most-linked pages. Limited in scope but direct from Google.
Ahrefs: The most comprehensive backlink index available. Site Explorer shows all backlinks, their DR, anchor text, and traffic estimates. Particularly useful for competitor analysis.
Moz Link Explorer: Shows Domain Authority, page authority, and backlink details.
SEMrush Backlink Analytics: Similar to Ahrefs with integrated keyword and competitor data.
Regular monitoring helps you catch lost links (so you can reclaim them), identify new links from potential partners, and detect any spammy links that may have targeted your site.
How to Earn High-Quality Backlinks
Earning quality backlinks requires a systematic approach:
Create Link-Worthy Content
The most reliable backlink magnet is content so useful, original, or data-rich that other sites want to reference it. Original research, comprehensive guides, free tools, and unique datasets all attract editorial links over time.
Guest Posting
Publish expert articles on authoritative sites in your niche. Each article typically earns one or more links back to your site. Focus on relevance and editorial quality.
Digital PR
Pitch original data, research findings, or expert commentary to journalists. A single feature in a major publication can earn dozens of links and significant referral traffic.
Broken Link Building
Find pages on authoritative sites that link to broken URLs (404 pages). Suggest your relevant content as a replacement. Website owners are often grateful for the fix.
Resource Page Outreach
Identify resource pages in your niche that curate helpful links. Contact the site owner and suggest your content for inclusion if it genuinely belongs.
Competitor Backlink Analysis
Use Ahrefs to see which sites link to your competitors. If they link to multiple competitors on similar topics, they may be interested in linking to your content too. See our guide on competitor backlinks analysis.
Frequently Asked Questions
How many backlinks do I need to rank?
Are nofollow backlinks worthless?
Can I buy backlinks safely?
What is a good number of backlinks per month to build?
Do internal links work like backlinks?
Conclusion
A backlink is one of the most powerful signals in search engine optimization. When authoritative sites link to your content, they transfer credibility and ranking power that helps your pages compete for high-value keywords.
Building a strong backlink profile requires patience and strategy: create genuinely useful content, pursue high-quality guest posting opportunities, use digital PR to earn editorial mentions, and analyze competitor link sources for outreach ideas. Avoid shortcuts like link buying that risk penalties.
Monitor your backlink profile regularly with tools like Ahrefs or Google Search Console, and address toxic links before they cause problems.
Related reading: What Is SEO Link Building | Best Link Building Strategies | What Is Anchor Text | Nofollow Backlinks and Their Role in SEO