Link building is the process of gaining links from other websites to one's own, known as backlinks. Google uses links to find new pages and as a signal of how relevant pages are,[1] and says the vast majority of new pages it discovers each day are found through links.[2] Links created mainly to manipulate rankings violate Google's spam policies.[3]
Links as a ranking signal
The use of links in ranking dates to Sergey Brin and Lawrence Page's 1998 Stanford paper, which described PageRank as a measure of a page's importance derived from the pages linking to it and argued that link anchor text often describes a page more accurately than the page itself.[4][5] Google says PageRank remains part of its core ranking systems, which analyze how pages link to each other to understand what they are about.[6]
Link spam
Google defines link spam as creating links primarily to manipulate rankings. Its examples include buying or selling links that pass ranking credit, excessive link exchanges, automated link creation, requiring links in contracts or terms of service, advertorials, guest posts or press releases with optimized links, low-quality directory or bookmark links, links embedded in widely distributed widgets or site-wide footers, and optimized links in forum comments.[3] Paid links are allowed if they are marked nofollow or sponsored.[3]
Link attributes
Site owners qualify outbound links with rel attributes:[7]
| Attribute | Use |
|---|---|
sponsored | Advertisements and paid links |
ugc | User-generated content such as comments and forum posts |
nofollow | Other links the site does not want associated with it |
Values can be combined, such as rel="ugc nofollow".[7] Google introduced sponsored and ugc in September 2019 and began treating all three as hints rather than strict directives.[8]
Penguin
In April 2012 Google launched an algorithm change, later known as Penguin, that lowered rankings for sites violating its guidelines, citing link schemes; it affected about 3.1% of English queries.[9] In September 2016 Google made Penguin part of its core algorithm, running in real time and adjusting rankings based on spam signals rather than demoting whole sites.[10] Google now lists Penguin as a retired system and names SpamBrain as its current spam-detection system.[6]
Disavowing links
Google's disavow tool lets site owners ask Google to ignore specific links to their site. Google says most sites do not need it and recommends it only when a site has many spammy links that have caused, or are likely to cause, a manual action, after first trying to have those links removed. It describes the tool as an advanced feature that can harm search performance if misused.[11]
Earning links
Google says links from other sites usually come over time as people discover useful content, and that site owners can also promote their sites through word of mouth, community involvement, social media and offline promotion, while warning that over-promotion can be treated as manipulation.[2] It recommends descriptive, concise anchor text without stuffed keywords.[1]
References
- ^ ^ "Link best practices for Google". Google Search Central, updated December 10, 2025. developers.google.com
- ^ ^ "Search Engine Optimization (SEO) Starter Guide". Google Search Central, updated December 10, 2025. developers.google.com
- ^ ^ ^ "Spam Policies for Google Web Search". Google Search Central, updated August 28, 2026. developers.google.com
- ^ Brin, Sergey; Page, Lawrence (1998). "The Anatomy of a Large-Scale Hypertextual Web Search Engine". Computer Networks 30: 107–117 (via Google Research). research.google
- ^ Brin, Sergey; Page, Lawrence (1998). "The Anatomy of a Large-Scale Hypertextual Web Search Engine (full text)". Stanford University (mirror, University of Ioannina). cs.uoi.gr
- ^ ^ "A guide to Google Search ranking systems". Google Search Central, updated December 10, 2025. developers.google.com
- ^ ^ "Qualify your outbound links to Google". Google Search Central, updated December 10, 2025. developers.google.com
- ^ Sullivan, Danny; Illyes, Gary (September 10, 2019). "Evolving "nofollow" – new ways to identify the nature of links". Google Search Central Blog. developers.google.com
- ^ Cutts, Matt (April 24, 2012). "Another step to reward high-quality sites". Google Search Central Blog. developers.google.com
- ^ Illyes, Gary (September 23, 2016). "Penguin is now part of our core algorithm". Google Search Central Blog. developers.google.com
- ^ "Disavow links to your site". Search Console Help. support.google.com