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A backlink for a given web resource is a link from some other website (the referrer) to that web resource (the referent). A web resource may be (for example) a website, web page, or web directory.
A backlink is a reference comparable to a citation. The quantity and sources of backlinks for a web page are among the factors that Google's PageRank algorithm evaluates in order to estimate how important the page is. The PageRank score is, in turn, one of the variables that Google Search uses to determine how high a web page should go in search results. This weighting of backlinks is analogous to citation analysis of books, scholarly papers, and academic journals.
Some other words for backlink are incoming link, inbound link, inlink, inward link, and sitation.
Search engine rankings
Search engines often use the number of backlinks that a website has as one of the most important factors for determining that website's search engine ranking, popularity and importance. Google's description of its PageRank system, for instance, notes that "Google interprets a link from page A to page B as a vote, by page A, for page B." Knowledge of this form of search engine rankings has fueled a portion of the SEO industry commonly termed linkspam, where a company attempts to place as many inbound links as possible to their site regardless of the context of the originating site. The significance of Search Engine rankings is pretty high, and it is regarded as a crucial parameter in online business and the conversion rate of visitors to any website, particularly when it comes to online shopping.
Websites often employ SEO techniques to increase the number of backlinks pointing to their website. Some methods are free for use by everyone whereas some methods, like linkbaiting, require quite a bit of planning and marketing to work. There are also paid techniques to increase the number of backlinks to a target site. For example, private blog networks can be used to purchase backlinks.
There are several factors that determine the value of a backlink. Backlinks from authoritative sites on a given topic are highly valuable. If both sites have content geared toward the keyword topic, the backlink is considered relevant and believed to have strong influence on the search engine rankings of the web page granted the backlink. A backlink represents a favorable 'editorial vote' for the receiving webpage from another granting webpage. Another important factor is the anchor text of the backlink. Anchor text is the descriptive labeling of the hyperlink as it appears on a web page. Search engine bots (i.e., spiders, crawlers, etc.) examine the anchor text to evaluate how relevant it is to the content on a webpage. Anchor text and webpage content congruency are highly weighted in search engine results page (SERP) rankings of a webpage with respect to any given keyword query by a search engine user.
Changes to the algorithms that produce search engine rankings can place a heightened focus on relevance to a particular topic. While some backlinks might be from sources containing highly valuable metrics, they could also be unrelated to the consumer's query or interest. An example of this would be a link from a popular shoe blog (with valuable metrics) to a site selling vintage pencil sharpeners. While the link appears valuable, it provides little to the consumer in terms of relevance.
When hypertext markup language (HTML) was designed, there was no explicit mechanism in the design to keep track of backlinks in software, as this carried additional logistical and network overhead.
Most content management systems include features to track backlinks, provided the external site linking in sends notification to the target site. Most wiki systems include the capability of determining what pages link internally to any given page, but do not track external links to any given page.
Other mechanisms have been developed to track backlinks between disparate webpages controlled by organizations that are not associated with each other. The most notable example of this is TrackBacks between blogs. Tools exist to determine who links to a particular domain, what anchor text they are using, and value of those links.
- Link farms
- Methods of website linking
- Search engine optimization
- Search engine results page
- Björneborn, Lennart; Ingwersen, Peter (2004). "Toward a Basic Framework for Webometrics". Journal of the American Society for Information Science and Technology 55 (14): 1218. doi:10.1002/asi.20077. Archived from the original on 2014-08-18.
- "About Search". Google. Archived from the original on 2011-11-04. Retrieved 2016-04-20.
- Lingras, Pawan; Akerkar, Rajendra (10 March 2010). "Web Structure Mining § PageRank Algorithm". Building an Intelligent Web: Theory and Practice. Jones & Bartlett Publishers. p. 294. ISBN 978-1-4496-6322-3.
- Olsen, Martin (20 May 2010). "Maximizing PageRank with New Backlinks". In Diaz, Josep; Calamoneri, Tiziana. Algorithms and Complexity: 7th International Conference, CIAC 2010, Rome, Italy, May 26–28, 2010, Proceedings. Berlin: Springer Science & Business Media. p. 37. ISBN 978-3-642-13072-4. OCLC 873382847.
- "Google's overview of PageRank". Retrieved 6 October 2014.