||This article may contain original research. (May 2012)|
Google Penguin is a code name for a Google algorithm update that was first announced on April 24, 2012. The update is aimed at decreasing search engine rankings of websites that violate Google’s Webmaster Guidelines by using now declared black-hat SEO techniques, such as keyword stuffing, cloaking, participating in link schemes, deliberate creation of duplicate content, and others. Unlike PageRank, however, Google makes all updates to this algorithm public.
Naming the algorithm update 
The Penguin update went live on April 24, 2012. However, Google did not announce an official name for it until two days later.
Penguin’s effect on Google search results 
By Google’s estimates, Penguin affects approximately 3.1% of search queries in English, about 3% of queries in languages like German, Chinese, and Arabic, and an even bigger percentage of them in "highly spammed" languages. On May 25, 2012, Google unveiled another Penguin update, called Penguin 1.1. This update, according to Matt Cutts, was supposed to affect less than one-tenth of a percent of English searches. The guiding principle for the update was to penalize websites using manipulative techniques to achieve high rankings. The purpose per Google was to catch excessive spammers, but it seems some legitimate sites and SEOs have been caught with this latest algorithm change. Few websites lost search rankings on Google for specific keywords during the Panda and Penguin rollouts. It appears anchor text was to blame in these cases, as the links pointing to these sites concentrated on only one or a few keywords while the content of the websites was satisfactory. As the update focused on the quality of backlinks, so the result varied for different websites. Some sites lost rankings for everything while some sites lost rankings on only specific keywords. One affected site had too many doorway pages with city/state pages. Google specifically mentions that doorway pages, which are only built to attract search engine traffic, are against their webmaster guidelines. Regardless, many people still use this technique. Penguin 3 was released Oct. 5, 2012 and affected 0.3% of queries.Google internal team uses different numbering for its Penguin updates despite what others are calling them. 
The difference between Penguin and previous updates 
Before Penguin, Google released a series of algorithm updates called Panda with the first appearing in February 2011. Panda aimed at downranking websites that provided poor user experience. The algorithm follows the logic by which Google’s human quality raters determine a website’s quality.
The strategic goal that Panda, Penguin, and page layout update share is to display higher quality websites at the top of Google’s search results. However, sites that were downranked as the result of these updates have different sets of characteristics. The main target of Google Penguin is spamdexing (including link bombing).
Google’s Penguin feedback form 
Two days after Penguin update was released Google prepared a feedback form, designed for two categories of users: those who want to report web spam that still ranks highly after the search algorithm change, and those who think that their site got unfairly hit by the update. Google also has a reconsideration form through Google Webmaster Tools for the 700,000 sites. Matt Cutts explained that over 600,000 of them were about black hat and less than 25,000 about unnatural links.
See also 
- The Penguin Update: Google's Webspam Algorithm Gets Official Name
- Webmaster Guidelines - Webmaster Tools Help
- Keyword stuffing - Webmaster Tools Help
- Link schemes - Webmaster Tools Help
- Duplicate content - Webmaster Tools Help
- "Keeping track of Penguin updates". 20 February 2013. Retrieved 29 April 2013.
- Barry Schwartz (20 February 2013). "No, Google Hasn’t Released Unannounced Penguin Updates". Retrieved 29 April 2013.
- Another step to reward high-quality sites - Inside Search
- Search Engine Watch
- Tracking Google Penguin 2.0: The Sky is Falling
- Infographic: The Google Panda Update, One Year Later
- How Google Uses Human Raters in Organic Search - SEW
- Official Google Webmaster Central Blog: Page layout algorithm improvement
- Browser Size - Google Labs
- Penguin Update Peck Your Site By Mistake? Google's Got A Form For That