Link farming is a questionable search engine optimization (SEO) tactic in which a website enters a relationship of reciprocal linking with another site or pays a provider for a large number of inbound links. Because many search engines use inbound links as a factor in determining a website's page rank, websites use link farming to boost their rankings in search engine results.
Although relevant inbound links are an important component of website SEO, this should not be confused with listing a site on a link farm, which does nothing more than link to other sites in a group.
Search engines such as Google view link farming as a form of spam. Google and others have implemented procedures to punish sites that gain inbound links through farms, rather than organically or through link campaigns with other high-quality sites.
Service providers who promise to improve a website's search engine rank may use link farming. In this situation, the provider simply posts links en masse on other unrelated websites, some of which are designed only for this purpose.
Search engines used to be very vulnerable to link farming because they primarily operated on the reasoning that a page has greater authority if a large number of other sites link to it. Now, link farming often fails because search engines have evolved to rank results based on what will be most useful for the user. This means that a link from a site with trusted content or similar content to the page to which it is linking is worth more than random links from many sites.
If webmasters try to inflate the number of backlinks to their website artificially through link farming, search engines generally punish this behavior when they detect it. A violation may result in a site's page rank being dropped or even removed for a time.
In essence, search engines attempt to encourage websites to gain authority – and thus page rank – in the most legitimate way possible. The ideal way to gain page rank is to create websites with great content that will be frequently linked to by other high-quality sites.