WordPress (WP, or WordPress.org) is a web content management system. It was originally created as a tool to publish blogs but has evolved to support publishing other web content, including more traditional websites, mailing lists, Internet forums, media galleries, membership sites, learning management systems, and online stores. Available as free and open-source software, WordPress is among the most popular content management systems – it was used by 22.52% of the top one million websites as of December 2024^[update].

WordPress is written in the PHP programming language and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system, known as “themes”. Since 2018, WordPress has included a block-based editor (“Gutenberg”).

To function, WordPress has to be installed on a web server, either as part of an Internet hosting service or on a personal computer.

WordPress was first released on May 27, 2003, by its founders, American developer Matt Mullenweg and English developer Mike Little. The WordPress Foundation owns WordPress, WordPress projects, and other related trademarks.

"WordPress is a factory that makes webpages" is a core analogy designed to clarify the functions of WordPress: it stores content and enables a user to create and publish webpages, requiring nothing beyond a domain and a hosting service.

WordPress has a web template system using a template processor. Its architecture is a front controller, routing all requests for non-static URIs to a single PHP file that parses the URI and identifies the target page. This allows support for more human-readable permalinks.

WordPress users may install and switch among many different themes. Themes allow users to change the look and functionality of a WordPress website without altering the core code or site content. Custom code can be added to the website by using a child theme or through a code editor. Every WordPress website requires at least one theme to be present. Themes may be directly installed using the WordPress "Appearance" administration tool in the dashboard, or theme folders may be copied directly into the themes directory. WordPress themes are generally classified into two categories: free and premium. Many free themes are listed in the WordPress theme directory (also known as the repository), and premium themes are available for purchase from marketplaces and individual WordPress developers. WordPress users may also create and develop their own custom themes and upload them in the WordPress directory or repository.

WordPress' plugin architecture allows users to extend or depreciate the features and functionality of a website or blog. As of December 2021^[update], WordPress.org has 59,756 plugins available, each of which offers custom functions and features enabling users to tailor their sites to their specific needs. However, this does not include the available premium plugins (approximately 1,500+), which may not be listed in the WordPress.org repository. These customizations range from search engine optimization (SEO) to client portals used to display private information to logged-in users, to content management systems, to content displaying features, such as the addition of widgets and navigation bars. 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. If the plugin developer has not tested the plugin with the last two major versions of WordPress, a warning message will be displayed on the plugin directory, informing users that the plugin may not work properly with the latest WordPress version. Most plugins are available through WordPress themselves, either via downloading them and installing the files manually via FTP or through the WordPress dashboard. However, many third parties offer plugins through their websites, many of which are paid packages.