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, quality, and relevance of backlinks for a web page are among the factors that search engines like Google evaluate in order to estimate how important the page is. PageRank calculates the score for each web page based on how all the web pages are connected among themselves, and is 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. A Topical PageRank has been researched and implemented as well, which gives more weight to backlinks coming from the page of a same topic as a target page.
Some other words for backlink are incoming link, inbound link, inlink, inward link, and citation.
Backlinks are offered in Wikis, but usually only within the bounds of the Wiki itself and enabled by the database backend. MediaWiki, specifically offers the "What links here" tool, some older Wikis, especially the first WikiWikiWeb, had the backlink functionality exposed in the page title.
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 (January 1998), for instance, noted 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. In January 2017, Google launched Penguin 4 update which devalued such link spam practices.
The significance of search engine rankings is 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. Blog commenting, guest blogging, article submission, press release distribution, social media engagements, and forum posting can be used to increase backlinks.
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. It has been estimated that the average cost of buying a link in 2019 was $291.55 and $391.55, when marketing blogs were excluded from the calculation.
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 and pages have content geared toward the 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. Backlinks can be generated by submissions, such as directory submissions, forum submission, social bookmarking, business listing, blog submissions, etc. 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.
- Björneborn, Lennart; Ingwersen, Peter (2004). "Toward a Basic Framework for Webometrics". Journal of the Association for Information Science and Technology. 55 (14): 1218. CiteSeerX 10.1.1.94.1691. doi:10.1002/asi.20077. Archived from the original on 2014-09-10. Retrieved 2020-05-27.
- Goh, Dion; Foo, Schubert (2007). Social Information Retrieval Systems: Emerging Technologies and Applications for Searching the Web Effectively: Emerging Technologies and Applications for Searching the Web Effectively. Information Science Reference. p. 132. ISBN 978-1-59904-543-6.
- "About Search". 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 (eds.). 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.
- Nie, Lan; Davison, Brian D.; Qi, Xiaoguang (2006). Topical Link Analysis for Web Search. Proceedings of the 29th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval. SIGIR '06. New York, NY, USA: ACM. pp. 91–98. doi:10.1145/1148170.1148189. ISBN 978-1595933690. S2CID 2877831.
- Sáez-Trumper, Diego (2020-04-16). "Open data and COVID-19: Wikipedia as an informational resource during the pandemic". Medium. Retrieved 2020-05-27.
- Ebersbach, Anja; Glaser, Markus; Heigl, Richard (2006). Wiki: Web Collaboration. Springer-Verlag Berlin Heidelberg. p. 111. doi:10.1007/3-540-29267-5. ISBN 978-3-540-25995-4.
- Jones, Kristopher (2018-01-24). "How to Push Great Content that Isn't Ranking Well". searchenginejournal.com. Retrieved 2020-05-27.
- "Google's overview of PageRank" (PDF). Retrieved 6 October 2014.
- Misra, Parth (2017-01-27). "The Invisible Threat of 'Black Hat' SEO to Your Company's Reputation". Entrepreneur. Retrieved 2020-05-27.
- Chasinov, Nick (2019-04-05). "How Entrepreneurs Can Beat Amazon at Organic Search". Entrepreneur. Retrieved 2020-05-27.
- Taylor, Gabriela (2013). Give Your Marketing a Digital Edge. Global & Digital. p. 171. ISBN 978-1-909924-30-7.
- Bucciachio, Vincent (2019-12-08). "What's the Cost of Buying Links in 2020? We Contacted 1,950 Blogs to Uncover the Truth". sociallyinfused.com. Retrieved 2020-05-27.
- Griffin, Fran (2019-06-07). "What does the modern PR professional look like in 2019?". PRWeek. Retrieved 2020-05-27.
- Loop, Matthew (2016). Social Media Made Me Rich: Here's How it Can do the Same for You. Morgan James Publishing. p. 129. ISBN 978-1-63047-793-6.
- Glazier, Alan (2011). Searchial Marketing:: How Social Media Drives Search Optimization in Web 3.0. Author House. p. 80. ISBN 978-1-4567-3892-1.