Search engine opti­miza­tion (SEO) is the process of improv­ing the vol­ume or qual­ity of traf­fic to a web site or a web page (such as a blog) from search engines via “nat­ural” or un-paid (”organic” or “algo­rith­mic”) search results as opposed to other forms of search engine mar­ket­ing (SEM) which may deal with paid inclu­sion. The the­ory is that the ear­lier (or higher) a site appears in the search results list, the more vis­i­tors it will receive from the search engine. SEO may tar­get dif­fer­ent kinds of search, includ­ing image search, local search, video search and industry-specific ver­ti­cal search engines. This gives a web site web pres­ence.

As an Inter­net mar­ket­ing strat­egy, SEO con­sid­ers how search engines work and what peo­ple search for. Opti­miz­ing a web­site pri­mar­ily involves edit­ing its con­tent and HTML and asso­ci­ated cod­ing to both increase its rel­e­vance to spe­cific key­words and to remove bar­ri­ers to the index­ing activ­i­ties of search engines.

The acronym “SEO” can refer to “search engine opti­miz­ers,” a term adopted by an indus­try of con­sul­tants who carry out opti­miza­tion projects on behalf of clients, and by employ­ees who per­form SEO ser­vices in-house. Search engine opti­miz­ers may offer SEO as a stand-alone ser­vice or as a part of a broader mar­ket­ing cam­paign. Because effec­tive SEO may require changes to the HTML source code of a site, SEO tac­tics may be incor­po­rated into web site devel­op­ment and design. The term “search engine friendly” may be used to describe web site designs, menus, con­tent man­age­ment sys­tems, images, videos, shop­ping carts, and other ele­ments that have been opti­mized for the pur­pose of search engine exposure.

Another class of tech­niques, known as black hat SEO or spamdex­ing, uses meth­ods such as link farms, key­word stuff­ing and arti­cle spin­ning that degrade both the rel­e­vance of search results and the user-experience of search engines. Search engines look for sites that employ these tech­niques in order to remove them from their indices.