What Is a Backlink? Definition, Types, and Why They Matter for SEO
A backlink (also called an inbound link) is any link from one website pointing to a page on a different website. Search engines have historically treated backlinks as a signal of trust and popularity — a site being linked to by others can act like a vote of confidence. Google's own documentation confirms links remain one of several factors it uses to help understand and rank content, though the company has repeatedly cautioned against artificial link-building schemes designed purely to manipulate rankings.
Definition
A backlink is created whenever one webpage contains a hyperlink to another webpage on a different domain. From the perspective of the page being linked to, it's called an inbound link or backlink; from the perspective of the linking page, it's called an outbound link. The overall pattern of backlinks pointing to a site is sometimes referred to as its link profile. Established
Why Backlinks Matter
Search engines originally used the density and quality of backlinks as a core proxy for authority — the idea being that if many reputable sites link to a page, that page is more likely to be a useful, trustworthy resource. Google's documentation continues to list links among the categories of information its systems use, alongside factors like content relevance and page usability, though it has never published the exact numerical weight links carry in any given ranking system. Established
Dofollow vs. Nofollow vs. Sponsored vs. UGC
| Attribute | Meaning |
|---|---|
| (none) / dofollow | The default. No rel attribute is added; the link can pass ranking signals normally. |
| rel="nofollow" | Originally meant "don't pass ranking credit." Since 2019, Google treats it as a hint rather than a strict directive. |
| rel="sponsored" | Google-recommended attribute for paid or advertising links, disclosing the commercial relationship. |
| rel="ugc" | Google-recommended attribute for user-generated content links, such as forum posts or blog comments. |
Google introduced the sponsored and ugc attributes in 2019 as hints, explaining that all three (nofollow, sponsored, ugc) may optionally be used by its systems as signals for crawling and indexing, rather than as absolute rules that always block credit from being passed. Established
What Makes a Backlink Valuable
- Relevance. A link from a site covering a related topic is generally considered more meaningful than one from an unrelated industry.
- The linking site's own authority and trust. A link from a well-established, reputable domain tends to carry more weight than one from a low-quality or spammy site.
- Editorial placement. Links earned naturally within genuine editorial content are treated differently than links inserted purely for SEO purposes.
- Anchor text. The clickable text of the link can provide additional context about the destination page's topic.
Link Schemes Google Warns Against
Google's spam policies explicitly list link schemes — buying or selling links that pass ranking credit, excessive link exchanges, and large-scale automated link-building — as violations that can lead to ranking demotions or manual actions. This is distinct from natural links that a site earns through genuinely useful content being referenced by others. Established
Common Mistakes
- Chasing link quantity over relevance and quality. A handful of relevant, reputable backlinks is generally worth more than a large volume of low-quality ones.
- Buying links without proper disclosure. Paid links that pass ranking credit without a
rel="sponsored"attribute violate Google's guidelines. - Ignoring the linking page's own trustworthiness. A backlink from a spammy or unrelated site can be neutral or even a liability, not automatically a benefit.
- Assuming nofollow links have zero value. Since 2019, Google treats nofollow as a hint, and nofollow links can still drive referral traffic and visibility regardless of their ranking effect.
FAQ
Do backlinks still matter for SEO?
Yes. Google's own documentation continues to list links among the signals its ranking systems consider, though the exact weighting isn't published and content quality and relevance also matter significantly.
Is a nofollow link worthless?
No. Since 2019, Google treats nofollow as a hint rather than a strict rule, meaning it may still be used as a signal in some cases. Nofollow links can also still generate direct referral traffic.
Is buying backlinks against Google's rules?
Yes, if the paid link is intended to pass ranking credit without being properly disclosed via rel="sponsored". Google's spam policies classify this as a link scheme.
Related Concepts
Sources
- Google Search Central. "How Search Works." developers.google.com
- Google Search Central. "Qualify Outbound Links to Third-Party Sites." developers.google.com
- Google Search Central. "Spam Policies for Google Web Search — Link Spam." developers.google.com