A backlink is a link from one website to another, and in SEO it acts as an external signal that can help search engines discover pages and judge their credibility. For site owners reviewing SEO quality, backlinks matter because they influence how easily important pages get crawled, how trustworthy a site appears, and which pages are most likely to compete for valuable search terms.
What a backlink tells search engines
Search engines use backlinks as one of many signals to understand page importance. A link from a relevant, established page can pass context and authority, while a link from a weak or unrelated page may add little value. Backlinks also help crawlers find new URLs, especially when internal linking is weak or a page is not prominently linked from navigation.
When checking a website, look beyond raw link counts. A smaller number of relevant backlinks from pages that get indexed and visited is usually more useful than a large volume of low-quality links. The linking page, anchor text, surrounding content, and placement on the page all affect how meaningful the backlink is.
How backlinks affect SEO checks
Backlinks are useful during an SEO review because they help explain why one page ranks while another does not. If a service page has strong content and sound technical setup but no external links, it may struggle against competitors with better link equity. If a page has many backlinks but remains invisible, the issue may be elsewhere, such as indexing, search intent mismatch, weak on-page optimization, or cannibalization.
- Check whether key commercial or informational pages have any referring domains.
- Review link relevance, not just quantity.
- Compare backlinks to competing pages ranking for the same query.
- Watch for unnatural patterns such as sitewide footer links or spam-heavy referring pages.
Practical example from a page audit
Imagine a local roofing company has a detailed roof repair page that is indexed but stuck on page two. A backlink review shows that competing pages have links from local news stories, supplier directories, and homeowner association resources, while the roofing page has none. In that case, the gap is not only content depth; it is external validation. Earning a few relevant links from local business associations or supplier partner pages could strengthen that page more than rewriting the copy again.
What to improve next if backlinks are weak
If a site lacks backlinks, start with pages that deserve them: original guides, useful tools, location pages with unique proof, or category pages tied to real demand. Then check if those pages are indexable, internally linked, and worth citing. Link building works better when the destination page is already technically sound and clearly aligned with a search need. During an SEO check, backlinks should be reviewed alongside indexing, internal links, content quality, and page intent, not as a standalone metric.