Link farm

On the World Wide Web, a link farm is any group of web sites that all hyperlink to every other site in the group. In graph theoretic terms, a link farm is a clique. Although some link farms can be created by hand, most are created through automated programs and services. A link farm is a form of spamming the index of a web search engine (sometimes called spamdexing). Other link exchange systems are designed to allow individual websites to selectively exchange links with other relevant websites and are not considered a form of spamdexing.

Search engines require ways to confirm page relevancy. A known method is to examine for one-way links coming directly from relevant websites. The process of building links should not be confused with being listed on link farms, as the latter requires reciprocal return links, which often renders the overall backlink advantage useless. This is due to oscillation, causing confusion over which is the vendor site and which is the promoting site.

Link farms were developed by search engine optimizers (SEOs) in 1999 to take advantage of the Inktomi search engine's dependence upon link popularity. Although link popularity is used by some search engines to help establish a ranking order for search results, the Inktomi engine at the time maintained two indexes. Search results were produced from the primary index which was limited to approximately 100 million listings. Pages with few inbound links fell out of the Inktomi index on a monthly basis.

Inktomi was targeted for manipulation through link farms because it was then used by several independent but popular search engines. Yahoo!, then the most popular search service also used Inktomi results to supplement its directory search feature. The link farms helped stabilize listings primarily for online business Web sites that had few natural links from larger, more stable sites in the Inktomi index.

Link farm exchanges were at first handled on an informal basis, but several service companies were founded to provide automated registration, categorization, and link page updates to member Web sites.

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