A link farm is a group of web sites that all link to each other and is a form of search engine spam. Link farms exploit the process where search engines look for links to and from sites to define a webpage’s authority.

Search engines will look to see if website A links to B which links back. They will look to see if websites A, B and C have links in common with each other.

Really, a link farm can be defined as any indiscriminate link exchange method that seeks to manipulate search engine authority. Link farms have been around for a long time, and although some link farms can be created by hand, most are created through automated programs and services. Search engines have countered link farms by identifying key attributes of link farms and removing those pages from the results. In some cases, entire domains were removed from the search engine indexes in order to prevent them from influencing search results.

What are link farms?

• Any indiscriminate link exchange, particularly when they are automated
• Websites that encourage links in, in exchange for something (preferential treatment etc.)
• Websites that manipulate PageRank by blocking a search engine’s access to link exchange pages

What link farms are not:

• Link exchanges. Reciprocal link exchange, when done properly, is actively encouraged by Google
• Link Bait. Encouraging people to link to you because you have interesting content is a key SEO tactic
• Pages that link to lots of other pages. If you have an authority page on the top 100 Irish Dancing websites, then that page is not a link farm and could easily become an authority on your topic.
• Where you have 10,000 links in and no links out. Whilst that would be a questionable use of resources, having a lot of useless links in is not going to see you get canned, and is not link spam.
• Tools that allow you to generate links out. Websites like Wikipedia and Alexa allow you to create thousands of interlinked pages, and pages that link out. As they are manually controlled, and are not automated link exchanges, then it is seen as ok.

In order to avoid falling into a Link Farm trap, Google recommends that websites focus on links from trustworthy sites within their own niche. According to Google, a site that participates in a link farm may have its search rankings penalized. Links from related sites carry more weight than those from irrelevant sites.