What are SEO backlinks?

When another website links to yours, its HTML contains an anchor tag pointing at your URL. Crawlers follow the tag, record the connection, and add it to Google's link graph, a map of which pages point where across the whole web. Your backlink profile is simply every inbound edge on that map.

Three parts of each link matter: the linking page (where the link lives), the anchor text (the clickable words), and the target (which page on your site receives the link). All three feed into how much value passes.

PageRank, the algorithm Google was founded on, treats each link as a vote and weights the vote by the authority of the voter. A link from a page that itself attracts strong links passes more value than one from an obscure corner of the web. Google stopped showing public PageRank scores years ago, but the concept still underpins ranking, which is why Ahrefs built Domain Rating and Moz built Domain Authority as visible stand-ins.

The other half of the story is enforcement. Penguin began penalizing manipulative link profiles in 2012 and, from 2016, switched to mostly devaluing spammy links. The link spam updates of 2021 and December 2022 took that further: SpamBrain identifies unnatural links and neutralizes them, so they simply pass nothing. Modern link building is mostly about avoiding links Google will ignore.

Most SEO backlinks fall into a handful of buckets, and the bucket predicts the value:

• Editorial links: placed by a journalist or editor because your content or expertise earned the citation. The highest-value class, and the only kind we build. See editorial backlinks for the deep dive.
• Guest post links: you write an article for another site and link back to yours. Ranges from legitimate to pure link farming depending on the host.
• Directory and profile links: business listings and social profiles. Fine for completeness, close to zero ranking value.
• Paid placements: against Google's policies unless tagged rel="sponsored", and the tag removes the ranking value you paid for.
• User-generated links: forum posts, comments, wiki edits. Typically tagged rel="ugc" and heavily discounted.

Five factors separate SEO backlinks that move rankings from links that merely exist. Relevance: a link from a site in your topic area counts for more than a stronger site in an unrelated one. Authority: the linking domain's own link profile, which DR and DA approximate. Traffic: sites with readers tend to pass more trust than metric-inflated shells. Placement: a link inside body copy beats one in a footer or author bio. Uniqueness: your tenth link from the same domain adds far less than your first from a new one, which is why referring domains are the number to track.

Weighing those factors takes practice, which is why a structured backlink quality checklist beats gut feel when you evaluate a vendor or a guest post target.

These beliefs waste beginners' budgets:

• "More backlinks means higher rankings." Ten links from respected publications can outweigh a thousand directory submissions. Count referring domains and their quality.
• "Domain Authority is a Google metric." DA belongs to Moz and DR to Ahrefs. Google uses neither. They're useful estimates, and sellers inflate them constantly.
• "Nofollow links are worthless." Google has treated nofollow as a hint since 2019, and nofollow coverage still drives referral traffic and brand discovery.
• "Good content earns links by itself." In competitive niches the best page with no promotion often stays invisible. Someone has to put it in front of people who can link.
• "Cheap links are a shortcut." Links from private blog networks get neutralized or worse. The shortcut leads back to the starting line, minus the budget. White hat link building covers the tactics that hold up.