What is Google Penguin?
Google Penguin was an algorithm update that demoted the rankings of sites engaged in manipulative link-building schemes. The update targeted sites with many low-quality backlinks and sites that engaged in keyword stuffing.
In a blog post announcing the update, Google mentioned that Penguin would affect sites that engaged in subtle spamming practices that are hard to detect without deeply analyzing the webpage. These sites appear to engage in white hat SEO on the surface but will be uncovered as web spam on closer inspection.
Google released the first Penguin update on April 24, 2012, and released several updates until September 23, 2016, when it mentioned that Penguin became part of its core algorithm.