WordPress's plugin architecture allows users to extend its features. WordPress has over 30,000 plugins available,[12] each of which offers custom functions and features enabling users to tailor their sites to their specific needs. These customizations range from search engine optimization, to client portals[13] used to display private information to logged in users, to content displaying features, such as the addition of widgets and navigation bars. But not all available plugins are always abreast with the upgrades and as a result they may not function properly or may not function at all.[14]