What is a backlink?
A backlink is a link on another website that points to a page on yours. Search engines read it as a vote and as a description of your page, but how much it counts depends on who links, where the link sits and what it says.
In short
- A backlink is a hyperlink on someone else's site that points to yours, and a referring domain is a separate website with at least one such link.
- Referring domains correlate with rankings slightly better than raw backlink counts, at 0.255 against 0.248 in Ahrefs' January 2025 study of one million keywords.
- A "dofollow" link is simply a normal link with no nofollow, sponsored or ugc label, and Google has treated those three labels as hints since 2019.
- Google's spam policies list widely distributed footer and template links as link spam, so placement inside the main text matters.
- Most poor links are ignored rather than punished, which means the usual cost of a bad link is the money spent on it.
A backlink is a hyperlink on another website that points to a page on yours. You will also see it called an inbound link or an inlink. To a search engine it carries two messages: the linking site is willing to send its readers to you, and the words of the link say something about what your page covers.
Not every backlink counts the same, and some do not count at all. The rest of this lesson explains the vocabulary and the features that separate a useful link from a wasted one.
Backlinks and referring domains
A referring domain is a separate website that links to you at least once. If one blog links to you 100 times, you have 100 backlinks and one referring domain.
The distinction matters because the first link from a site says much more than the fiftieth. In Ahrefs’ study of one million US keywords, published in January 2025, the number of referring domains correlated with rankings at 0.255, slightly ahead of the raw number of backlinks at 0.248. Most link builders therefore count referring domains, not links.
A correlation is not proof of cause. Pages that rank well also attract links because more people see them.
What a link tells a search engine
An exhibit from the US antitrust case against Google, reported in May 2025, shows links working in two places.
- Trust. The exhibit describes PageRank as “a single signal relating to distance from a known good source”, used as an input to a quality score for the site.
- Relevance. Anchors, the clickable words of links, are one of three core relevance signals alongside the body text of the page and user clicks.
So a backlink can raise trust in your whole site and, separately, help one page rank for the topic named in the anchor. How search engines evaluate links covers this in detail.
Followed, nofollow, sponsored and ugc
A normal link has no special label. People call it a “dofollow” or followed link, although no such attribute exists in HTML.
A site can add one of three labels to a link: nofollow (we do not vouch for this), sponsored (this was paid for) and ugc (a user added this, as in a comment). Since 2019 Google has read all three as hints, so it decides for itself whether to use the link.
In Ahrefs’ 2025 study, followed referring domains correlated with rankings at 0.250 and all referring domains at 0.255. The two numbers are too close to tell whether labelled links pass value. A natural link profile contains both kinds. The full detail is in link attributes: nofollow, sponsored and ugc.
What makes a backlink valuable
The exact weights are not public. The table sets out the features that Google’s own documents, court exhibits and the 2024 leak point to, with a note on how firm each one is.
| Feature | What to look for | How firm the evidence is |
|---|---|---|
| Authority of the source | The linking site is itself linked to by trusted sites | Confirmed. The court exhibit describes PageRank as distance from a known good source |
| Relevance | The linking page and site cover your topic | Strong in direction. Google’s guidance and several leaked fields agree, but no weighting is known |
| Placement | The link sits in the main text, where a reader would click it | Strong in direction. Google’s spam policies name footer and template links as link spam |
| Anchor text | The words describe the target page honestly | Confirmed as a relevance signal. Heavy keyword anchors are also the classic spam pattern |
| Editorial choice | A person at the site decided to link, with no payment or contract | This is the line Google’s spam policy draws |
| Indexed source page | The linking page is in Google’s index | Logical requirement. A link on a page Google has not indexed is unlikely to count |
| A new domain | The site has not linked to you before | Supported by the Ahrefs correlation above |
Two features are often overrated. A high Domain Rating or Domain Authority on the linking site is a third-party estimate, not something Google uses, and it says nothing about the specific page that links to you. See Domain Authority vs Domain Rating. The second is the label. A nofollow link from a publication your customers read can be worth more to the business than a followed link from a site nobody visits.
What makes a backlink worthless or risky
Google defines link spam as creating links “primarily for the purpose of manipulating search rankings”. Its spam policies, last updated in August 2026, give examples that include:
- buying or selling links for ranking purposes, including sending a product in exchange for a link
- excessive link exchanges
- links created by automated programs
- low-quality directory or bookmark site links
- forum comments with optimised links in the post or signature
- widely distributed links in footers or templates
Buying a link for advertising is allowed when it is labelled sponsored or nofollow.
Since the Penguin update became part of the core algorithm, Google has mostly ignored such links instead of punishing the site. A manual action, applied by a human reviewer and shown in Search Console, still exists for profiles dominated by manipulative links. Google link penalties and recovery explains both.
The idea that every weak link is “toxic” and must be disavowed is a different matter. Google’s John Mueller has called toxic links a concept made up by SEO tools, and Google’s guidance limits the disavow tool to sites with a manual action or a large number of links they built or paid for themselves.
How to see your own backlinks
Google Search Console has a Links report. It is free and comes from Google itself, but it shows a sample, not the full list. Ahrefs, Semrush and Majestic each crawl the web with their own bots and report what they find. Their numbers differ from each other and from Google’s because each index is different.
When you review a link, open the page it sits on. A two-minute look at the page tells you more than any score: is the page indexed, is the link in the main text, and does the site look like something a real audience reads?
Where to go next
Read link attributes for the labels, then anchor text for the words of the link. If you are about to pay for a placement, start with how to vet a publisher.
Common questions
What is the difference between a backlink and a referring domain?
A backlink is one link. A referring domain is one website that links to you, however many times. One hundred links from the same site count as one referring domain.
Are all backlinks good for SEO?
No. Google says it neutralises links it considers manipulative, which means they are ignored. A profile dominated by bought or automated links can also lead to a manual action.
What is a dofollow backlink?
It is an informal name for an ordinary link that carries no nofollow, sponsored or ugc attribute. There is no "dofollow" attribute in HTML.
How can I see who links to my site?
The Links report in Google Search Console shows a sample of the links Google knows about. Third-party tools such as Ahrefs, Semrush and Majestic run their own crawlers and usually show more, but none of them sees everything.