WordPress is open source software for building websites and blogs, written in PHP and working with a MySQL or MariaDB database. It began in 2003 as a fork of b2/cafelog by Mike Little and Matt Mullenweg and is released under the GPL (version 2 or later). In this self-hosted form you install WordPress yourself on a web server, at a hosting provider or on your own computer, and adapt it as needed. This is distinct from WordPress.com, a separate commercial hosting service run by Automattic.
The software is largely developed by a community but is closely associated with Automattic, the US company of founder Mullenweg, based in San Francisco. The WordPress Foundation, a non-profit with 501(c)(3) status, owns the trademarks. In 2024 a dispute with the hosting company WP Engine led to a lawsuit. Because you host it yourself, you decide where the data sits, and hosting with a European provider keeps it within the EU.