What is a backlink?
A backlink is simply a link from one website to another. Search engines treat each one as a vote of confidence — which is why backlinks are one of the strongest signals in SEO.
Updated 5 August 2026
The basic idea
When website A links to website B, that link is a backlinkfor B. Search engines read the web as a giant graph of these links and use them to judge which pages are trusted. In effect, every backlink is a recommendation: “this page is worth visiting.”
Why backlinks matter so much
Google's original breakthrough was ranking pages by their links, and links remain one of the top-ranking signals decades later. The logic is simple: anyone can claim their page is great, but a link from a respected site is hard to fake at scale. That is why domain authority — a score built almost entirely from backlinks — tracks so closely with ranking ability.
What makes a good backlink
- Authority of the source. A link from a central, trusted domain carries the weight of everything behind it.
- Relevance. A link from a site in your topic counts for more than one from an unrelated site.
- Follow vs nofollow. A normal (“dofollow”) link passes authority; a nofollow link does not, though it still has value for traffic and brand.
- Placement. A link inside real content beats one buried in a footer or a low-quality directory.
How many backlinks the average site really has
We measured 7.1 billion links across 118 million domains. The reality is humbling: the median linked website has just two referring domains, and 13% of all domains have no discoverable inbound links at all. A handful of good links puts you ahead of most of the web. See the full picture in our web-wide link study.
How to check your backlinks
Paste any domain into our free backlink checker to see which domains link to it, sorted by how strong each one is — no signup. To find sites that link to your competitors but not to you, use the link intersect tool.
See any site's backlinks — free
Frequently asked questions
How many backlinks do I need to rank?
There is no fixed number — it depends on your competition and the quality of the links. For perspective, the median linked website has just two referring domains, and having 20 already puts you ahead of about 97% of the web. Quality matters far more than count.
What is the difference between a backlink and a referring domain?
A backlink is a single link. A referring domain is a unique website linking to you, no matter how many times it links. One referring domain might send you 500 backlinks from 500 pages — but it still counts as one source of trust.
Are all backlinks good?
No. A link from a strong, relevant site helps; a link from a spammy or unrelated site does little or can even hurt. Links marked 'nofollow' pass no ranking authority, though they can still bring traffic.