Search engine optimization (SEO) can be defined as the process of improving the visibility of a website (or a webpage) in search engines’ search results. The concept is that the higher and more frequently a website is ranked in search results, the greater the chance that visitors will see the website and click to access it. SEO can be applied in different kinds of searches (e.g., news search, image search, local search, video search, academic search). This entry provides an overview of SEO and then examines its history, common SEO strategies, the dominance of Google search, and the advantages of SEO.