How do backlinks work?
Links still matter, and most of what is written about them is either out of date or written by someone selling them. This is what Google actually says.
Last updated
Quick answer
A backlink is a link from another website to yours. Google uses links to find new pages and as a signal of what pages are about and how relevant they are; its PageRank system, which weighs links, is still part of its core ranking systems. A relevant link from a site your customers trust counts for far more than many links from unrelated sites, and links created mainly to manipulate rankings break Google's spam policies.
Key takeaways
- Google uses links for discovery and as a relevance signal.
- One relevant, editorial link beats many unrelated ones.
- Paid links are allowed only when marked sponsored or nofollow.
- Most sites never need the disavow tool.
What a backlink is and why Google counts it
Google says it uses links as a signal when determining the relevancy of pages and to find new pages to crawl. Its ranking systems guide names PageRank, one of the systems used when Google launched, and says it continues to be part of its core ranking systems, though how it works has evolved a lot.
How a link is found, then weighed
- DiscoveryGoogle crawls a page that links to yours and finds your URL through the link.
- FollowingIf the link is a normal link and isn't marked nofollow, sponsored or ugc, Google generally follows it.
- ContextThe anchor text and the surrounding content tell Google what your page is about.
- WeightingThe link's value depends on the linking page: how relevant and trusted it is.
What makes one link worth more than another
- Relevance: a link from a site in your industry or area says more than one from an unrelated site.
- Editorial choice: a link someone chose to give is worth more than one you placed yourself.
- Placement: a link within the body of useful content counts for more than one in a footer or a list of hundreds.
- Anchor text: Google describes good anchor text as descriptive, reasonably concise and relevant to both pages.
- Referring domains: ten links from ten different sites generally say more than ten links from one site.
Authority scores from SEO tools, such as domain rating, are those tools' estimates. Google doesn't use them.
Nofollow, sponsored and ugc links
Google's guidance on qualifying outbound links defines three rel values. Links with them are generally not followed, though the linked page may still be crawled another way.
| Attribute | Use it for | Example |
|---|---|---|
| rel="sponsored" | Advertisements and paid placements | A paid listing or sponsored post |
| rel="ugc" | User-generated content | Links in comments and forum posts |
| rel="nofollow" | Other links you don't want to vouch for | A link you can't vouch for |
Values can be combined, such as rel="ugc nofollow". There's no "dofollow" attribute: a link without these values is simply a normal link.
Link types by value and risk
| Link type | Typical value | Risk |
|---|---|---|
| Editorial mention in relevant content | High | Low |
| Supplier, partner or industry body listing | Moderate, and locally relevant | Low |
| Genuine local or industry directory | Low to moderate | Low |
| Sponsorship, marked sponsored | Mostly brand value | Low when qualified |
| Guest post written for the link | Low | High if the links are optimised |
| Bought links, link exchanges, link networks | None worth having | High: link spam |
What Google calls link spam
Google's spam policies define link spam as creating links to or from a site primarily to manipulate search rankings. The examples Google gives include buying or selling links, excessive link exchanges, automated programs that create links, low-quality directory and bookmark links, keyword-rich links hidden in widgets or footers, forum signature links, and advertorials or guest posts with optimised links that aren't qualified.
Paid links aren't a violation in themselves, as long as they're qualified with sponsored or nofollow.
Bad links and the disavow tool
Google's disavow documentation says most sites will not need it. It's meant for sites with a considerable number of spammy, artificial or low-quality links that have caused a manual action, or likely will, and Google warns that using it incorrectly can harm a site's performance.
If you haven't bought links and haven't had a manual action, a few odd links pointing at your site are normal and can be left alone.
How links are earned without risk
- Create something people in your industry want to reference: original data, a useful tool or a clear guide.
- Ask suppliers, manufacturers and partners for the listing they give stockists or members.
- Join industry bodies and local business associations that list members.
- Answer journalists and local media with genuine expertise.
- Mark any paid sponsorship link as sponsored.
Common questions
How many backlinks do I need to rank?
There's no number. It depends on how many and how good the links to the pages you're competing with are, which is why competitor analysis looks at the ranking page.
Can a page rank without backlinks?
Yes, for specific searches with little competition, especially local ones. Competitive searches usually need some.
Do nofollow links help SEO?
Google says links with nofollow, sponsored or ugc are generally not followed. They can still bring visitors and attention, which is often how followed links come later.
Is buying backlinks against Google's rules?
Buying links that pass ranking credit is link spam under Google's spam policies. Paid links are fine when marked sponsored or nofollow.
Should I disavow bad backlinks?
Usually not. Google says most sites won't need the disavow tool; it's for a considerable number of artificial links that have caused, or will likely cause, a manual action.
What's the difference between a backlink and a referring domain?
A backlink is one link; a referring domain is one site linking to you, however many links it has. Ten links from one site are one referring domain.
How long do backlinks take to affect rankings?
Google doesn't give a timeframe. A link has to be crawled first, and the effect depends on the link and the competition.
Where to next
If you would rather have someone do this than read about it, the commercial page for this work is Link building services.