Link farming is one of the most popular forms of Black Hat SEO used in the past. It is a form of spamdexing in which any group of websites are used by other websites to get links. However, other than as a form of spamdexing, other link farms or link exchange systems are designed to allow individual websites to selectively exchange links with other relevant websites, which are not considered a form of spamming. So what is a link farm?

Brief History of Link Farm Use
The first link farm was formulated by several SEO consultants in 1999 as to take advantage of the Inktomi search engine's dependence upon link popularity. Inktomi was primarily targeted mainly because it was used by several of that time's popular search engines such as HotBot as well as Yahoo! which used Inktomi results to supplement its directory search feature. Other than Inktomi, link farming was also used for Google which is known for its different approach to indexing.

Google's algorithm isn't only depended on the number of inbound links, but more about the weight of every links called PageRank. According to SEO Philippines consultants, the PageRank algorithm determines that some links may be more valuable than others, and therefore assigns them more weight than others. Link farming was then adapted to help increase the PageRank of member pages.

Fall of Link Farming
Link farms begun to become a form of spamdexing when members have started to manipulate link farming sites. Some webmasters that joined the services, received inbound linkage, and then found ways to hide their outbound links or to avoid posting any links on their sites at all. Search engines countered the link farm movement by identifying specific attributes associated with link farm pages and filtering those pages from indexing and search results. Google have released several guidelines in acquiring links. They recommend that webmasters should request relevant link and avoid link farms. According to SEO Philippines consultants, a site that participates in a link farm may have its search rankings penalized.

The justification for link farm-influenced crawling diminished proportionately as the search engines expanded their capacities to index more sites. Once the 500-million listing threshold was crossed, link farms became unnecessary for helping sites stay in primary indexes. Inktomi's technology, now a part of Yahoo!, now indexes billions of Web pages and uses them to offer its search results.

According to SEO Philippines consultants, although most search engines today have come to use the same algorithm that Google uses, such as Ask.com, MSN, and Yahoo!, link farms are still popular as a way to increase PageRank or perceived equivalent values.