Link building is the practice of getting other websites to link to yours. That is the whole definition. Everything else, guest posts, directory listings, digital PR, broken-link outreach, is just a tactic for doing that one thing. Before getting into whether it works, it helps to be precise about what is actually being counted.
Backlink vs. referring domain: they are not the same number
A backlink is a single link from one page to yours. A referring domain is a distinct website that links to you at least once, no matter how many individual links it contains. One site can give you 50 backlinks from 50 different blog posts, and that still counts as one referring domain.
Referring domain count matters more than raw backlink count. A hundred links from one low-quality site is one data point. A hundred links from a hundred different real sites is a hundred independent signals. Most serious link-authority research, including Stackra's own, measures referring domains for exactly this reason.
Dofollow vs. nofollow
By default, a link passes some amount of authority from the linking page to the linked page. Adding rel="nofollow" to a link tells search engines to treat it differently, historically as a signal to not pass that authority through. Comment sections, paid placements, and user-generated content are commonly marked nofollow. In practice, major search engines now treat nofollow as a hint rather than a strict rule, so a nofollow link is not worthless, but it is not equivalent to an untagged link either.
Does link building actually work?
This is the part most explainers skip entirely, because most of them are written by people selling link building. Stackra tracked Common Crawl's link-authority data against Chrome traffic data across 9.68 million domains over three years, then checked the finding against a paid commercial backlink tool on 500 real businesses. Going from 0-5 referring domains to 1,000+ takes a site from a 7% to an 83% chance of reaching real traffic, and that gap survives controlling for age, industry, CMS, and schema markup (a controlled model scores 0.928 out of a possible 1.0). The short version: real links from real, relevant sites do correlate with better traffic outcomes, especially for a genuine business with real substance behind it. But manufacturing a link spike with no real traffic or business behind it fails almost every time. Among 60,291 sites that tried exactly that, tested 12 different ways, 99.6%+ never reached meaningful traffic.
The common link-building tactics, briefly
The tactics range from slow and durable to fast and fragile.
- •Digital PR and original research: publishing something genuinely newsworthy or data-backed that other sites choose to cite. Slow, but the links are real and durable.
- •Guest posting: writing content for another site in exchange for a link back. Works when the site is relevant and the content is genuinely useful; becomes spam when done at volume on irrelevant sites.
- •Directory and listing submissions: getting listed on relevant industry or local directories. Low effort, modest but real value, especially for local businesses.
- •Broken-link outreach: finding dead links on other sites and suggesting your own content as a replacement. Works, but scales slowly since it depends on manual outreach.
- •Buying links or link packages: paying for placement, often at volume, often on sites with no real audience. This is the tactic our data shows failing 99.6%+ of the time when there is no real business behind it.
What this means if you are deciding where to spend effort
Link building is not a scam and it is not useless, but the causality runs differently than most pitches imply. Links tend to follow a business worth visiting, not the other way around. If you are weighing whether to pay for link building specifically, or trying to evaluate a pitch you already received, the decision-focused breakdown below walks through what the data says to actually look for.
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Frequently asked questions
Common questions about link building basics.
What is link building in SEO?
Link building is the practice of getting other websites to link to yours, usually with the goal of increasing a site's perceived authority and, in theory, its search visibility. Tactics range from digital PR and guest posting to directory listings and buying placements outright.
What are referring domains?
A referring domain is a distinct website that links to yours at least once. It is different from a raw backlink count, which counts every individual link, even multiple links from the same site. Referring domain count is the more meaningful number because each one represents an independent site vouching for yours.
Is link building still effective in 2026?
Real, organic links from relevant sites do correlate with better traffic outcomes, based on Stackra's analysis of 5 million websites over 3 years. But links manufactured without a real business behind them fail at a 99.6%+ rate. The effect is real for genuine sites; it is not a shortcut.
What is the difference between a dofollow and nofollow link?
A standard link passes some authority from the linking page. A nofollow link carries a tag telling search engines to treat it differently, historically to not pass that authority through. Search engines now treat nofollow as a hint rather than an absolute rule, so nofollow links still carry some value, just less certainty than an untagged link.