What Is a Backlink? A Plain-English Guide for SEO

A backlink is a hyperlink on one website that points to a page on a different website. Search engines treat backlinks as a signal that other sites vouch for the linked page, which is why the number and quality of a page’s backlinks remains one of the clearest correlates with how well it ranks. Not every backlink carries equal weight: the rel attribute on the link, the anchor text used, and the trustworthiness of the linking page all determine how much of that signal actually passes through.

The Anatomy of a Backlink: Source Page, Anchor Text, and Rel Attribute

Every backlink is made of three parts, and each one changes how much it’s worth.

The source page is the page carrying the link. Its own authority and topical relevance pass through to the page it links to. Backlinko’s guidance is blunt about this: “Google will put MUCH more weight on links from sites about marathons, running, fitness vs. sites about fishing, unicycles, and digital marketing.” A link from an established site in your niche is worth more than the same link from an unrelated one.

The anchor text is the clickable, visible text of the link. It gives both readers and search engines context about the destination page’s topic, which is why an anchor like “backlink audit checklist” tells Google more than a bare “click here.” Anchor text leaning too heavily on exact-match keywords across many links is itself a spam signal, which is what Google’s Penguin update was built to catch.

The rel attribute is the HTML instruction that classifies the relationship: unmarked (the historical “dofollow”), nofollow, sponsored, or ugc. Google’s own documentation is specific about when to use each one, instructing site owners to mark “links that are advertisements or paid placements … with the sponsored value,” to mark “user-generated content (UGC) links, such as comments and forum posts, with the ugc value,” and to “use the nofollow value when other values don’t apply.”

Why Backlinks Still Move Rankings

Backlink volume alone doesn’t decide who ranks first, but the correlation between backlinks and position has held up across two decades of ranking updates. The number one result in Google carries almost four times as many backlinks as pages ranking two through ten, and the number of unique referring domains linking to a page correlates with rankings more than any other single backlink metric, according to Backlinko’s ranking research.

Competitiveness changes how many links that takes. Ahrefs’ data puts the benchmark for ranking in the top 10 for a broad term like “tea” at roughly 756 unique backlinks, while a specific, low-competition long-tail query can rank with a handful of relevant links or none at all. That gap is also why link-building advice built for a national brand rarely translates to a local service business: the keyword’s competitiveness sets the bar, not a universal backlink count.

Good Backlinks vs. Toxic Backlinks: What Separates Them

Signal	Healthy backlink	Risky or toxic backlink
Topical relevance	From a page or site in the same niche or an adjacent topic	From an unrelated site with no topical connection
Rel attribute	Reflects the real relationship (unmarked for an editorial endorsement, sponsored for paid, ugc for user content)	An undisclosed paid placement dressed up as an editorial link
Anchor text	A natural mix of branded, generic, and partial-match anchors	Heavy repetition of the same exact-match keyword anchor across many links
Source page quality	Indexed, gets its own organic traffic, has original content	Thin, auto-generated, or part of a private blog network
Placement	Sits inside the body content, in context	Buried in a footer, sidebar, or site-wide widget repeated across hundreds of pages

Google’s spam policies define link spam as “the practice of creating links to or from a site primarily for the purpose of manipulating search rankings,” and list buying or selling links, excessive link exchanges, and automated link-creation programs as examples. The same policy draws a clear line for paid links: they are “not a violation” as long as they are “qualified with a rel=”nofollow” or rel=”sponsored” attribute value.” A link that fails one row in the table above rarely causes a problem on its own. A pattern of them across a profile is exactly what triggers algorithmic link-spam filtering or a manual action.

Dofollow, Nofollow, Sponsored, and UGC: What Each Attribute Tells Google

The four rel states aren’t interchangeable, and mixing them up is one of the more common mistakes in a backlink profile. Since September 2019, Google has treated nofollow, sponsored, and ugc as “hints about which links to consider for ranking purposes” rather than as strict directives. That same announcement states that nofollow “will be treated as a hint on whether to crawl and index a page, rather than a directive,” which is a meaningfully softer stance than the attribute originally had.

In practice, an unmarked link is the closest thing to an editorial vote of confidence. A sponsored link tells Google the placement was paid for. A ugc link flags that a reader, not the site owner, added it. Getting this classification right on your own outbound links, and checking it on the inbound links you’ve earned, is covered in more depth in Dofollow vs. Nofollow Links: A Complete Guide to Link Attributes.

The Main Types of Backlinks You’ll Run Into

Beyond the dofollow, nofollow, sponsored, and ugc split, backlinks are commonly grouped by how they were earned: editorial links inside body content, guest post links, resource or directory page links, forum and comment links (almost always ugc), reciprocal links between two sites, and sitewide links repeated across every page of a domain, which typically carry less weight per link than a single in-context editorial mention. Types of Backlinks: The Complete Taxonomy (and Which Ones Actually Matter) breaks down which of these categories move the needle and which are mostly noise in a modern link profile.

Checking Whether the Backlinks You Have Are Actually Working

Earning a backlink is not the same as keeping it. Links get removed when a site redesigns, an old post gets deleted, a webmaster changes their mind about an unpaid mention, or an editor quietly switches a link from dofollow to nofollow after the fact. None of that shows up unless someone checks.

A simple four-point check catches most of what goes wrong with a backlink after you’ve earned it:

1. Is it still live? The source page still exists and returns a 200, not a 404 or a redirect to an unrelated page.
2. Is the rel attribute unchanged? A link that was unmarked (dofollow) when you got it hasn’t quietly become nofollow.
3. Is the anchor text unchanged? Some CMS migrations and template updates silently rewrite anchor text.
4. Is the source page still relevant? A site that pivoted to an unrelated niche, or got deindexed for spam, is passing less, or worse, than it did when you earned the link.

Running that check on a handful of links is a five-minute manual job. Running it on hundreds of links you built through outreach, or on a backlink export from Ahrefs, Semrush, or Google Search Console, is what BacklinkTower’s free tools are built for: drop in the export and get an instant per-link status check, anchor-text distribution, and dofollow/nofollow/sponsored/ugc classification, with a one-click disavow file for anything that reads as toxic. If you want that four-point check running automatically over time instead of only when you remember to run it, that’s what the paid monitoring layer covers: scheduled re-checks that alert you the moment a link drops, goes nofollow, 404s, or has its anchor changed. For a profile that has grown past a few dozen links, How to Do a Backlink Audit: A Step-by-Step Guide walks through the full process end to end.

Frequently Asked Questions