What Is a Backlink? Why Links Still Matter for SEO
A backlink is a link on one website that points to a page on another. Seen from the receiving site it is an inbound link. Backlinks still matter for SEO because a link from an independent site works like a citation: evidence, created by someone other than the page’s owner, that the page is worth pointing to. Search engines use that evidence alongside many other signals to judge which pages are useful and credible.
Why Links Still Count
Links were the foundation of Google’s earliest ranking, and they remain part of it. Google’s guide to its ranking systems describes several systems that use the links between pages to understand what pages are about and which may best answer a query, including PageRank, one of the core systems Google used at launch. Links are one input among many today, but they are one of the few that comes from outside the page itself.
What Makes One Link Worth More Than Another
| Factor | Why it matters |
|---|---|
| Relevance | A link from a site about a related subject is more plausibly a real endorsement than one from an unrelated site |
| Source reputation | A link from an established, respected site carries more evidence than one from a site that exists to host links |
| Placement | A link inside editorial content about the subject means more than one in a footer, sidebar, or long list of links |
| Anchor text | The clickable words describe the target page; the same commercial phrase repeated across many links is a manipulation pattern |
| Link attributes | Links marked <!–INLINECODE0–>, <!–INLINECODE1–>, or <!–INLINECODE2–> tell Google about the relationship behind them |
| Distinct domains | Links from many independent domains are more evidence than many links from one domain |
No published formula weights these factors. The direction is what can be stated: relevance, editorial placement, and source credibility matter more than the raw count.
Earned Links and Manufactured Ones
Links that hold up are given because the page earned them: original research, data, or tools that others cite; newsworthy stories picked up by publications; useful contributed articles; resource pages that list your page because it helps their readers.
Google’s spam policies target links created to manipulate rankings. The first example on the list is buying or selling links for ranking; others include excessive link exchanges, automated programs or services that create links, and keyword-rich anchors placed in articles, guest posts, or press releases published elsewhere. Paid placements are not banned; their links have to be qualified with sponsored or nofollow so they pass no ranking credit. In a 2021 post on qualifying links, Google asked sites in affiliate programs to qualify those links with rel="sponsored" and warned about campaigns of low-quality sponsored and guest posts “primarily intended to gain links.”
What Happens When Links Cross the Line
Google’s spam policies state: “Sites that violate our policies may rank lower in results or not appear in results at all.” Since 2016, the link spam system once known as Penguin has run in real time as part of the core algorithm, devaluing spam signals as pages are recrawled instead of waiting for a periodic update.
If a site’s profile is full of links it cannot get removed, for example after past paid link work, Google offers the disavow links tool. Google’s guidance says: “In most cases, Google can assess which links to trust without additional guidance, so most sites will not need to use this tool.” It reserves the tool for sites with a considerable number of spammy links that have caused, or are likely to cause, a manual action.
Judging a Link in Practice
- Is the linking site about a subject related to the page it links to?
- Does it have a real audience and reputation, or does it exist to publish outbound links?
- Is the link inside real content?
- Is the attribute right: none for an editorial citation,
sponsored(ornofollow) for paid,ugcfor user-submitted? - Would the link make sense to a reader if search engines did not exist?
Tools such as Ahrefs, Semrush, and Moz help review a link profile at scale: referring domains, anchor text, and links worth a closer look. Their scores are their own estimates. Google’s guidance on third-party SEO tools notes that such tools cannot see Google’s internal ranking data.
Questions About Backlinks
How many backlinks do I need?
There is no threshold. It depends on what the pages already ranking for your target searches have, and a few relevant links from respected sites can mean more than many weak ones.
Are nofollow links worthless?
No. Google treats nofollow as a hint, so it may or may not use such a link, and the attribute signals that the linking site is not vouching for the page. They also bring visitors, visibility, and sometimes the attention that leads to other links.